Plant Biology

Mitochondrion (plural, mitochondria)

(Gr. mitos, thread + chondrion, a grain) a small cytoplasmic particle associated with intracellular respiration

Monophyletic group

(Gr. mono, single + phyle, tribe) a group of organisms or taxa that includes an ancestor, all of its descendants, and nothing else

Monomer

(Gr. monos, single + meros, part) a single subunit that can be used to form a larger complex; for example, glucose, a simple sugar, is a monomer of a cellulose chain

Monostromatic

(Gr. monos, single, solitary + stroma, a bed, currently meaning a supporting framework) referring to a thallus, one cell in thickness

Monohybrid

(Gr. monos, solitary + L. hybrida, a mongrel) a cross involving one pair of contrasting characters

Monocotyledon

(Gr. monos, solitary + kotyledon, a cup-shaped hollow) a plant whose embryo has one cotyledon

Monoecious

(Gr. monos, solitary + oikos, house) referring to a plant that produces male and female gametes on the same individual; in contrast to dioecious, each individual being one sex only

Morphogenesis

(Gr. morphe, form + L. genitus, to produce) the structural and physiologic events involved in the development of an entire organism or part of an organism

Morphology

(Gr. morphe, form + logos, discourse) the study of form and its development

Mycorrhiza (plural, mycorrhizae)

(Gr. mykes, fungus + riza, root) a symbiotic association between a fungus and a root of a plant

Mycologist

(Gr. mykes, mushroom + logos, discourse) a scientist who specializes in the study of fungi

Mycelium

(Gr. mykes, mushroom) the branching network of hyphae forming the body of most fungi

Myxomycophyta

(Gr. myxa, mucus + mykes, mushroom + phyton, plant) a division comprising the "slime fungi"

Nectar

(Gr. nektar, drink of the gods) a fluid rich in sugars secreted by nectaries, which often are located near or in flowers

Nectary

(Gr. nektar, the drink of the gods) a nectar-secreting gland, found in flowers

Nyctinastic movement

(Gr. nyct, night + nastos, closepressed, firm) a movement of plant parts (for example, leaf petioles) associated with diurnal changes in temperature or light intensity

Ecology

(Gr. oikos, home + logos, discourse) the study of plant life in relation to the environment

Ecosystem

(Gr. oikos, house + synistanai, to place together) an inclusive term for a living community and all the factors of its nonliving environment

Ecotype

(Gr. oikos, house + typos, the mark of a blow) genetic variant within a species that is adapted to a particular environment, yet remains interfertile with all other members of the species

Oömycota

(Gr. oion, egg + mukes, fungus) a group of organisms typically classified as fungi but containing cellulose cell walls and other cellular details shared with several algal groups (golden algae, brown algae, diatoms); classified in this text with the Heterokonts; examples include the causes of downy mildew of grape, potato blight, and sudden oak death

Oligosaccharide

(Gr. oligos, small, few + sakcharon, sugar) a molecule consisting of a chain of 2 to 10 simple sugars (for example, glucose)

Osmosis

(Gr. osmos, a pushing) movement of a solvent through a differentially permeable membrane in response to a difference in solute concentration

Osmometer

(Gr. osmos, pushing + meter, measure) a devise for measuring the magnitude of osmotic force

Paleozoic

(Gr. palaios, ancient + zoe, life) a geologic era beginning 570 million years ago and ending 225 million years ago

Paleoecology

(Gr. palaios, ancient) a field of ecology that reconstructs past vegetation and climate from fossil evidence

Paleobotany

(Gr. palaios, ancient, prehistoric + botane, a plant) the study of fossil plants

Pangaea

(Gr. pan, whole + geo, Earth) a continuous landmass existing 250 million years ago, which contained all the continents that today are separated; the southern portion of this supercontinent is Gondwanaland and the northern portion is Laurasia

Paradermal section

(Gr. para, beside + derma, skin) a section cut parallel to a flat surface, such as a leaf section cut parallel to the surface of the blade

Paraphysis (plural, paraphyses)

(Gr. para, beside + physis, growth) a slender, multicellular hair (Fucus, and others); one of the sterile branches or hyphae growing beside fertile cells in the fruiting body of certain fungi

Parasexual cycle

(Gr. para, beside) a process by which mitosporic fungi sometimes achieve recombination without meiosis, involving formation of a heterokaryon followed by nuclear fusion and gradual return to the haploid state by loss of chromosomes

Parasite

(Gr. parasitos, one who eats at the table of another) an organism deriving its food from the living body of another organism

Phylogeny

(Gr. phylon, race or tribe + genesis, beginning) the series of changes by which a given taxon evolved from its ancestors

Phylum (plural, phyla)

(Gr. phylon, race or tribe) in the taxonomic hierarchy, a group of classes; also called a division

Physiology

(Gr. physis, nature + logos, discourse) the science of the functions and activities of living organisms

Plankton

(Gr. planktos, wandering) free-floating aquatic plants and animals, collectively

Plasma membrane

(Gr. plasma, anything formed + L. membrana, parchment) a delicate cytoplasmic membrane found on the outside of the protoplast adjacent to the cell wall

Plasmogamy

(Gr. plasma, anything molded or formed + gamos, marriage) the fusion of protoplasts, not accompanied by nuclear fusion

Plasmodesma (plural, plasmodesmata)

(Gr. plasma, something formed + desmos, a bond, a band) fine protoplasmic thread passing through the wall that separates two protoplasts

Plasmolysis

(Gr. plasma, something formed + lysis, a loosening) the separation of the cytoplasm from the cell wall caused by removal of water from the protoplast

Plasmodium

(Gr. plasma, something formed + mod. L. odium, something of the nature of) in Myxomycetes, a slimy mass of protoplasm, with no surrounding wall and with numerous free nuclei distributed throughout

Plasmid

(Gr. plasma, to form) a piece of extrachromosomal DNA, found in some bacteria

Plastid

(Gr. plastis, a builder) a cellular organelle in which carbohydrate metabolism is located

Pneumatophores

(Gr. pneuma, breath + phore, F. pherein, to carry) extensions of the root systems of some plants growing in swampy areas; in contrast to most roots, they are negatively geotropic and grow out of the water, thus assuring adequate aeration

Polarity

(Gr. pol, an axis) the observed differentiation of an organism, tissue, or cell into parts having opposed or contrasted properties or form

Polynomial

(Gr. polys, many + L. nomen, name) scientific name for an organism, composed of more than two words; see Binomial

Polymer

(Gr. polys, many + meros, part) a compound formed by repeating structural units; for example, cellulose is a polymer of glucose, a simple sugar

Polyploid

(Gr. polys, many + ploos, fold) referring to a plant, tissue, or cell with more than two complete sets of chromosomes, for example, 4n, 6n

Polyribosome

(Gr. polys, many + ribosomes) an aggregation of ribosomes, frequently simply called polysome

Polysaccharides

(Gr. polys, much, many + sakcharon, sugar) long-chain molecules composed of units (monomers) of a sugar; starch and cellulose are polysaccharides

Polynucleotides

(Gr. polys, much, many) long-chain molecules composed of units (monomers) called nucleotides; nucleic acid is a polynucleotide

Prokaryote

(Gr. pro, before + Gr. karyon, a nut, referring in modern biology to the nucleus) member of the domain Archaea or Bacteria; an organism that does not have its DNA in a nucleus, separated from the cytoplasm by an envelope

Prophase

(Gr. pro, before + phasis, appearance) an early stage in nuclear division, characterized by the shortening and thickening of the chromosomes and their movement to the metaphase plate

Proplastid

(Gr. pro, before + plastid) a type of plastid, occurring generally in meristematic cells, that will develop into a chloroplast

Prothallium

(Gr. pro, before + thallos, a sprout) in ferns, the haploid gametophyte generation

Proteins

(Gr. proteios, holding first place) naturally occurring complex organic substances, composed of one or more polypeptide chains, which through interactions among amino acids in different parts of the chain(s) acquire specific three-dimensional shapes required for their biological functions

Proterozoic

(Gr. protera, before in time + zoe, life) the earliest geologic era, beginning about 4.5 to 5 billion years ago and ending 570 million years ago; also called Precambrian era

Protista

(Gr. protistos, the very first) an artificial (nonmonophyletic) grouping of eukaryotic organisms that are not included in kingdoms Plantae, Fungi, or Animalia; organisms within it are called protists

Protoplast

(Gr. protoplastos, formed first) the organized living unit of a single cell; a cell from which the cell wall has been removed

Protoagriculture

(Gr. protos, first + L. ager, land + cultura, cultivation) a form of plant cultivation thought to precede agriculture, in which desireable plants are tended and selected for in their natural habitats rather than in prepared fields sown to monocultures

Protochlorophyll

(Gr. protos, first + chloros, green + phyllos, leaf) one of the precursors of chlorophyll; it accumulates in dark-grown and potentially green tissue

Protoderm

(Gr. protos, first + derma, skin) a primary meristem that gives rise to epidermis

Protonema (plural, protonemata)

(Gr. protos, first + nema, a thread) an algal-like filamentous growth; an early stage in development of the gametophyte of mosses

Protoplasm

(Gr. protos, first + plasma, something formed) living substance

Protoxylem

(Gr. protos, first + xylon, wood) first formed primary xylem

Proton

(Gr. protos, first) a positively charged particle found in the atomic nucleus of all elements; the number of protons in a nucleus determines the identity of the element; the mass of a proton is 1.67 x 10-24 g

Psilophytes

(Gr. psilos, bare) seedless vascular plants mainly consisting of bare, dichotomously branched green stems; the whisk ferns, Psilotum and Tmistris, which traditionally have been classified in their own division, the Psilophyta, but in this book are placed with horsetails, ophioglossalean ferns, marattialean ferns, and true ferns in the monilophyte lineage

Pseudopodium

(Gr. psuedes, false + podion, a foot) in Myxomycetes, an armlike projection from the body by which the plant creeps over the surface

Pyrenoid

(Gr. pyren, the stone of a fruit + L. oides, like) a denser body occurring within the chloroplasts of certain algae and liverworts and apparently associated with starch deposition

Rachis

(Gr. rhachis, a backbone) main axis of spike; axis of fern leaf (frond) from which pinnae arise; in compound leaves, the extension of the petiole corresponding to the midrib of an entire leaf

Raphe

(Gr. rhaphe, seam) ridge on seeds, formed by the stalk of the ovule, in those seeds in which the funiculus is sharply bent at the base of the ovule

Rhizoid

(Gr. rhiza, root + L. oides, like) in nonvascular plants, a filament of cells that lacks the vascular system of a root but performs rootlike functions (anchorage and absorption); in fungi, a hypha too narrow to house nuclei, functioning in anchorage, absorption, and sometimes mating

Rhizophores

(Gr. rhiza, root + phoros, bearing) leafless branches that grow downward from the leafy stems of certain Lycophyta and give rise to roots when they come into contact with the soil

Rhizome

(Gr. rhiza, root) an elongated, underground, horizontal stem

Saprobe

(Gr. sapros, rotten) an organism that derives its food from organic products released by another organism

Schizocarp

(Gr. schizein, to split + karpos, fruit) dry fruit with two or more united carpels that split apart at maturity

Sclerophyll

(Gr. scleros, hard + phullon, leaf) evergreen leaves having a hard texture, thick cuticle and blade, closely packed cells in the mesophyll region, low rate of photosynthesis, and a low rate of transpiration

Sclerenchyma

(Gr. skleros, hard + enchyma, a suffix denoting tissue) a strengthening tissue composed of cells with heavily lignified cell walls

Sclereids

(Gr. skleros, hard) cells of different shapes having heavily lignified cell walls

Sorus (plural, sori)

(Gr. soros, a heap) a grouping of sporangia; especially characteristic of ferns

Soredium (plural, soredia)

(Gr. soros, a heap) an asexual reproductive unit released by lichens, consisting of a few algal cells surrounded by fungal hyphae

Spermatophyte

(Gr. sperma, seed + phyton, plant) a seed plant

Sperm

(Gr. sperma, the generative substance or seed of a male animal) a male gamete

Life history pattern

a collection of traits that describe how a plant allocates time and energy throughout its life span so that it can occupy a habitat and reproduce successfully

Trophic level

(Gr. trophe, food) a group of organisms sharing the same food source, as producers, herbivores, consumers, or decomposers

Tylose (plural, tyloses)

(Gr. tylos, a lump or knot) a growth of one cell into the cavity of another

Xanthophyta

(Gr. xanthos, yellow) a small group of freshwater and (mainly) unicellular algae that contain chlorophylls a and c, have cellulose walls, and store carbohydrate as oil droplets; classified in this text with the protists in the heterokont group

Xanthophyll

(Gr. xanthos, yellowish brown + phyllon, leaf) a yellow chloroplast pigment

Xerophyte

(Gr. xeros, dry + phyton, a plant) a plant resistant to drought or that lives in dry places

Xylem

(Gr. xylon, wood) a plant tissue consisting of tracheids, vessel members, parenchyma cells, and fibers; wood

Zoology

(Gr. zoon, an animal + logos, speech) the science of animal life

Zoosporangium

(Gr. zoon, an animal + sporangium) a sporangium bearing zoospores

Zoospore

(Gr. zoon, an animal + spore) a eukaryotic spore that swims by means of one or more flagella

Zygomorphic

(Gr. zygo, yoke, pair + morphe, form) referring to bilateral symmetry; said of organisms, or a flower, capable of being divided into two symmetrical halves only by a single, longitudinal plane passing through the axis

Zygospore

(Gr. zygon, a yoke + spore) a resistant spore that contains one or more diploid zygote nuclei at some stage in its development

Zygote

(Gr. zygon, a yoke) a diploid cell resulting from the fusion of gametes or gametangia and their nuclei

Anions

(Gr.) a negatively charged ion, as hydroxide, chloride, or a protein with a net excess of negatively charged carboxylate functional groups

Cations

(Gr.) positively charged ions, such as sodium, potassium, and hydronium ions, and proteins with a net positive charge

Niche

(It. nicchia, a recess in a wall) the functional position of an organism in its ecosystem

Golgi apparatus

(Italian cytologist Camillo Golgi [1844-1926], who first described the organelle) in animal cells, a complex perinuclear region; in plant cells, a series of flattened bladders associated with packaging, secretion, or both

Alpine

(L. Alpes, the Alps Mountains) meadowlike vegetation at high elevation, above tree line

Semelparous

(L. Semele, a mythical woman who bore a child and then died + paritas, equal) a perennial plant that flowers only once, at the end of its life span

Amensalism

(L. a, not + mensa, table) a form of biological interaction in which one organism is inhibited by another, but the other is neither inhibited nor stimulated

Absorb

(L. ab, away + sorbere, to suck in) to suck up, to drink up, or to take in; in plant cells, materials are taken (absorbed) in solution

Abscission zone

(L. abscissus, cut off) zone of delicate, thin-walled cells extending across the base of a petiole, the breakdown of which disjoins the leaf or fruit from the stem

Adaptation

(L. ad, to + aptare, to fit) in evolution, a trait that evolved in response to directional selection and that enhances the success of the species in the selecting environment; also, the process of generating an adaptation; in physiology, adjustment of an organism to its environment

Aggregate fruit

(L. ad, to + gregare, to collect; to bring together) a fruit developing from the several separate carpels of a single flower; for example, a strawberry

Adsorption

(L. ad, to + sorbere, to suck in) the concentration of molecules or ions of a substance at a surface or an interface (boundary) between two substances

Adhesion

(L. adhaerere, to stick to) a sticking together of unlike things or materials

Adnation

(L. adnasci, to grow to) in flowers, the growing together of two or more whorls to a greater or lesser extent; compare Adhesion

Adventitious

(L. adventicius, not properly belonging to) referring to a structure arising from an unusual place: buds at other places than leaf axils, roots growing from stems or leaves

Alveolates

(L. alveus, small cavity) a group of protists that have membrane-bounded sacs lying beneath the plasma membrane; includes dinoflagellates, foraminifera, ciliates, and the apicomplexa

Amyloplast

(L. amylum, starch + plastos, formed) cytoplasmic organelle specialized to store starch; abundant in roots and in storage organs such as tubers

Animalia

(L. animalis, living) the animal kingdom

Annual

(L. annualis, within a year) a plant that completes its life cycle in one year and then dies

Annular vessels

(L. annularis, a ring) vessels with lignified rings of secondary wall material

Red tide

a coloring of offshore marine water caused by dense phytoplankton populations; often accompanied by toxic byproducts

Mildew

a common name for mold or fungi

Phospholipid

a complex lipid compound, composed of fatty acids, glycerol, phosphate, and one additional hydrophilic residue (for example, choline, serine, inositol); a bilayer of phospholipids is a major constituent of most biological membranes

Salt

a compound formed from a defined mixture of cations and anions

Reproductive isolation

a condition in which two populations cannot exchange genes

Vessel member

a conducting cell in the primary and secondary xylem; typically have a lignified secondary cell wall and open end walls, a perforation plate

Closed-cone conifer

a conifer (usually in the genera Pinus or Cupressus) that produces cones that neither open at maturity nor fall from the parent tree; the cone scales open only when exposed to an increased temperature, the exact temperature depending on the species

Nitrogen cycle

a continuous series of natural processes by which nitrogen passes through successive stations in air, soil, and organisms, involving principally ammonification, nitrogen fixation, nitrification, nitrate reduction, and denitrification

Cytoplasmic streaming

a controlled flow of cell contents along cytoskeletal elements from one part of a cell to another

Magnoliids

a core angiosperm group of (mainly) woody dicots, including magnolia, cinnamon, camphor, nutmeg, sassafras, avocado, betel nut, and ginger

Double bond

a covalent bond that involves four electrons

Energy pyramid

a diagram of total caloric energy in all the organisms within each trophic level, starting with producers on the bottom layer of the diagram and ending with tertiary consumers; each higher layer is smaller than the one below, so that the combination of layers look like a stepped pyramid

Phylogenetic tree

a diagrammatic representation of evolutionary relationships for a group of organisms; a cladogram is a type of phylogenetic tree

Pollen profile

a diagrammatic summary of the sequence and abundance of pollen types that have been chronologically trapped in sediments

Founder effect

a difference in allele ratio among populations that occurs when an offshoot population is founded by so few individuals that chance strongly affects which alleles of the parental population are present in the founders

Trait

a distinctive definable characteristic; a mark of individuality

Random plant distribution

a distribution pattern of a plant population within an area such that the probability of finding an individual at one point is the same for all points

Rosid clade

a diverse group of eudicots, including legumes, eucalypts, roses, mustards, and tropical melastomes

Annulus

(L. anulus or annulus, a ring) in ferns, a row of specialized cells in a sporangium, of importance in opening of the sporangium; in mosses, thick-walled cells along the rim of the sporangium to which the peristome is attached

Charophytes

a group of algae closely related to the chlorophytes, classified in this text as plants

Tissue

a group of cells of similar structure that performs a special function

Caryophyllid clade

a group of eudicots with small flowers that have superior ovaries; includes many succulents (ice plants, cacti) and also carnations, amaranths, buckwheat, spinach, and sugar beet

Compound pistil

a group of fused pistils

Gibberellins

a group of growth hormones, the most characteristic effect of which is to increase the elongation of stems in a number of kinds of higher plants

Purine

a group of organic bases having a double-ring structure, one five-carbon and the other six-carbon

Phenetic species

a group of organisms that is distinguished from other species on the basis of morphologic or molecular characters, or both, rather than mating tests; contrast with biological species

Biological species

a group of organisms, the members of which reproduce successfully only with other members of the same group and not with members of other groups

Softwood

a gymnosperm tree; having wood that is light and easier to work than the wood of an angiosperm

Female gametophyte

a haploid plant that forms eggs; in the flowering plant life cycle, the embryo sac

Male gametophyte

a haploid plant that forms sperm; in the flowering plant life cycle, the two-celled pollen grain

Molecular character

a hereditary chemical trait of an organism, such as the detailed structure of a gene, or the ability to make a particular kind of molecule

Morphologic character

a hereditary trait that is related to body form, such as flower color or shape

Septal pore

a hole through a septum in a hypha, permitting material to pass through; also called a perforation

Tritium

a hydrogen atom, the nucleus of which contains one proton and two neutrons; it is written as 3H; the more common hydrogen nucleus consists only of a proton

Clamp connection

a hyphal relic of events that maintain the dikaryotic condition in a basidiomycete mycelium, named for the relic's resemblance to a carpenter's clamp

Acid-growth hypothesis

a hypothesis to explain the stimulation of growth of plant cells by auxin; states that the main effect of auxin is to cause cells to secrete acid (H- ions) and that the acid stimulates the changes in plasticity

Apex

(L. apex, a tip, point, or extremity) the tip, point, or angular summit of anything: the tip of a leaf, that portion of a root or shoot containing apical and primary meristems

Aspect

(L. aspectus, appearance) the direction of slope of a surface, as a hillside with a south-facing aspect

Assimilation

(L. assimilare, to make like) the transformation of food into protoplasm

Auricles

(L. auricula, dim. of auris, ear) earlike structures; in grasses, small projections that grow out from the opposite side of the sheath at its upper end where it joins the blade

Bacillus

(L. baculum, a stick) a rod-shaped bacterium

Biennial

(L. biennium, a period of two years) a plant that requires two years to complete its life cycle; flowering is normally delayed until the second year

Binomial

(L. binominis, two names) the formal name given to a species, consisting of the genus name followed by a species epithet; also called the species name

Bract

(L. bractea, a thin plate of precious metal) a modified leaf, from the axil of which arises a flower or an inflorescence

Bulb

(L. bulbus, a modified bud, usually underground) a short, flattened, or disk-shaped underground stem, with many fleshy scale-leaves filled with stored food

Callose

(L. callum, thick skin + ose, a suffix indicating a carbohydrate) an amorphous carbohydrate deposited around pores in sieve-tube members and in other areas in cell walls

Callus

(L. callum, thick skin) mass of large, thin-walled cells, usually developed as the result of wounding

Calorie

(L. calor, heat) the amount of heat needed to increase the temperature of 1 g water 1°C (usually from 14.5 to 15.5°C), also called gram-calorie; 1,000 calories = 1 kilocalorie

Cambium

(L. cambium, one of the alimentary body fluids supposed to nourish the body organs) a layer, usually regarded as one or two cells in thickness, of persistently meristematic tissues, giving rise to secondary tissues, resulting in growth in diameter

Capillaries

(L. capillus, hair) very small spaces, or very fine bores in a tube

Capsule

(L. capsula, dim. of capsa, a case) in angiosperms, a simple, dry, dehiscent fruit, with two or more carpels; in mosses, a spore-producing structure with diploid photosynthetic tissue, capable of splitting open along slits or at an apical pore

Carnivore

(L. caro, flesh + vorare, to swallow up) an organism that obtains food by killing and consuming other organisms; normally refers to an animal that eats other animals, but the term also can be used for microbial protozoans or for an herbivorous animal that consumes entire plants or their seeds

Carotenoid

(L. carota, carrot) a reddish orange plastid pigment

Caruncle

(L. caruncula, dim. of caro, flesh, wart) a spongy outgrowth of the seed coat, especially prominent in the castor bean seed

Cell

(L. cella, small room) a structural and physiologic unit composed of living organisms, in which take place the majority of complicated reactions characteristic of life; it is surrounded by a plasma membrane, contains a metabolic system, and has a store of DNA

Cisterna (plural, cisternae)

(L. cistern, a reservoir) generally referring to sections of the endoplasmic reticulum that appear in electron micrographs as parallel membranes, each about 5 nm in thickness bounding a space about 40 nm in width

Class

(L. classis, one of the six divisions of Roman people) in the taxonomic hierarchy, a group that contains one or more orders

Coalescence

(L. coalescere, to grow together) a condition in which there is union of separate parts of any one whorl of flower parts; synonyms are Connation and Cohesion

Cohesion

(L. cohaerere, to stick together) union or holding together of parts of the same materials; the union of floral parts of the same whorl, as petals to petals

Colony

(L. colonia, a settlement) a growth form characterized by a group of closely associated, but poorly differentiated, cells; sometimes filaments can be associated together in a colony (as in Nostoc), but more typically unicells are associated in a colony

Community

(L. communitas, a fellowship) all the populations within a given habitat; usually the populations are thought of as being somewhat interdependent

Compensation depth

(L. compensare, to counterbalance) that depth, in a body of water, at which light intensity is so low that photosynthesis of floating or submerged plants just equals respiration

Compensation point

(L. compensare, to counterbalance) the light intensity (light compensation point) or the carbon dioxide concentration (CO2 compensation point) at which photosynthesis just equals respiration

Competition

(L. competere, to strive together) a form of biological interaction in which both organisms (at least initially) decline in growth or success because of the insufficient supply of some necessary factor(s)

Conceptacle

(L. conceptaculum, a receptacle) a cavity or chamber of a frond (of Fucus, for example) in which gametangia are borne

Conduction

(L. conducere, to bring together) act of moving or conveying a substance through the plant; generally the movement of water through the xylem or food through the phloem

Conjugation

(L. conjugatus, united) in algae, sexual reproduction accomplished by fusing isogametes; in bacteria, transfer of DNA from one bacterium to another bacterium of the same species

Connation

(L. connatus, to be born together) condition in a flower where there is a union of similar parts of any one whorl of appendages; synonym of Coalescence

Conservation

(L. conservare, to keep) in biology, the systematic protection of natural resources and species; also the study of techniques for protecting resources and species

Corolla

(L. corolla, dim. of corona, a wreath, crown) petals, collectively; usually the conspicuous colored flower whorl

Cortex

(L. cortex, bark) region of primary tissue in a stem or root bounded externally by the epidermis and internally in the stem by the phloem and in the root by the pericycle; develops from the primary meristem, the ground meristem

Cristae

(L. crista, a crest) crests or ridges, used here to designate the infoldings of the inner mitochondrial membrane

Cuticle

(L. cuticula, dim. of cutis, the skin) waxy layer on outer wall of epidermal cells

Cutin

(L. cutis, the skin) waxy substance that is but slightly permeable to water, water vapor, and gases

Decomposer

(L. de, from + componere, to put together) an organism that obtains food by breaking down dead organic matter into simpler molecules

Decomposition

(L. de, to denote an act undone + componere, to put together) a separation or dissolving into simpler compounds; rotting or decaying

Denitrification

(L. de, to denote an act undone + nitrum, nitro, a combining form indicating the presence of nitrogen + facere, to make) conversion of nitrates into nitrites, or into gaseous oxides of nitrogen, or even into free nitrogen

Deciduous

(L. deciduus, falling) referring to trees and shrubs that lose their leaves in the fall

Dehiscent

(L. dehiscere, to split open) opening spontaneously when ripe, splitting into definite parts

Deletion

(L. deletus, to destroy, to wipe out) used here to designate an area, or region, lacking from a chromosome

Determinate

(L. determinare, to limit) generally, having defined limits; in plant development, a morphogenetic process that ends with a cessation of cell division and growth

Detritus

(L. detritus, worn away) particulate organic matter released in the processes of decomposition of dead organisms or parts of organisms (such as plant litter)

Differentiation

(L. differre, to carry different ways) development from one cell to many cells, accompanied by a modification of the new cells for the performance of particular functions

Diffusion

(L. diffusus, spread out) the movement of molecules, and thus a substance, from a region of greater concentration of those molecules to a region of smaller concentration

Digestion

(L. digestio, dividing, or tearing into pieces, an orderly distribution) the processes of rendering food available for metabolism by breaking it down into simpler compounds, chiefly through actions of enzymes

Archegonium

(L. dim. of Gr. archegonos, literally a little founder of a race) female gametangium or egg-bearing organ, in which the egg is protected by a jacket of sterile cells

Oögonium

(L. dim. of Gr. oogonos, literally, a little egg layer) female gametangium of egg-bearing organ not protected by a jacket of sterile cells, characteristic of the thallophytes

Seaweed

a large alga that is differentiated into holdfast, stipe, and blade regions (except for some floating seaweeds that lack a holdfast); kelps are large seaweeds in the brown algae group

Asterid clade

a large number of herbaceous species (in many flowering plant families) that are the most highly specialized eudicots, including heaths, tomatoes and potatoes, mints, umbellifers, and sunflowers

Sun leaf

a leaf high in the canopy that receives high amounts of solar radiation

Shade leaf

a leaf lower in the canopy that receives less solar radiation

Compound leaf

a leaf whose blade is divided into several distinct leaflets

Sporic life cycle

a life cycle in which both gametophyte and sporophyte generations are multicellular organisms

Gametic life cycle

a life cycle in which only the gametes are haploid, all other phases being diploid

Zygotic life cycle

a life cycle in which the only diploid phase is the single-celled zygote

C type life history

a life history pattern that describes long-lived, large, competitive plants; similar to kselected plants

S type life history

a life history pattern that describes long-lived, slow-growing plants of varying adult size, which live in habitats too stressful for R- or C-type plants; plants that have unusual metabolic or morphologic traits that mitigate environmental stresses

R type life hisory

a life history pattern that describes short-lived, small plants that often live in frequently disturbed habitats; similar to r-selected plants

Bacteriochlorophyll

a light-harvesting pigment found in certain bacteria; the molecular structure is similar to that of chlorophyll a, but certain side groups and the absorption spectrum are unique

Protochlorophyllide holochrome

a light-sensitive compound or complex composed of photochlorophyll and a protein; absorption of light converts the protochlorophyll part to chlorophyll

Monilophytes

a lineage of seedless vascular plants separate from the lycophytes; once more diverse and abundant in the Carboniferous period (Coal Age), and now represented by herbs such as horsetails, whisk ferns, ophioglossalean ferns, marattialean ferns, and true ferns

Lycophytes

a lineage of seedless vascular plants separate from the monilophytes; once highly diverse and dominant in the Carboniferous period (Coal Age), and now represented by herbs such as Lycopodium, Selaginella, and Isoetes

Polypeptide chain

a linear polymer formed from amino acids held together by peptide bonds

Triglyceride

a lipid compound composed of three fatty acids and glycerol; usually functions as a form of stored carbon and energy

Sieve cells

a long and slender sieve element found in the phloem of gymnosperms and some ferns, often associated with a specialized parenchyma-like albuminous cell, with relatively unspecialized sieve areas and with tapering end walls that lack sieve plates

Algin

a long-chain polymer of mannuronic acid found in the cell walls of the brown algae

Nectar guide

a mark of contrasting color or texture that may serve to guide pollinators to nectaries within the flower

Apical meristem

a mass of dividing cells at the very tip of a shoot or root

p protein

a mass of protein material formerly called slime found in sieve-tube members

Population genetics

a mathematically based discipline that extends the study of genetics to include evolution

Backcross

a mating in which a hybrid organism mates with a member of one of the hybrid's parental types

Ballistospore release

a mechanism of active meiospore release found only in basidiomycete fungi, based on physical forces that arise from merging a water droplet with a water film

Osmotic pump

a mechanism of forcing solution through a pipe (for example, sieve tube) using osmosis to generate pressure at one end

Eukaryote

a member of the Eukarya

Lysosomes

a membrane-bound body within a cell, containing enzymes that when released destroy the cytoplasmic components of the cell

Electron transport chain

a membrane-bound series of electron carriers that controls the flow of electrons from reduced to oxidized compounds, so that some of the energy carried by the electrons is used to form ATP; the chain consists of several compounds (carriers) that alternately accept and donate electrons; found in mitochondria and chloroplasts

Cork cambium

a meristem that forms the periderm; synonym for phellogen

Vacuole

(L. dim. of vacuus, empty) an organelle of a plant cell, surrounded and differentiated from the rest of the cytoplasm by the tonoplast membrane and containing various substances depending on the type of cell

Pinnule

(L. diminutive of pinna, little feather) a leaflet of a leaflet; the ultimate "leaf" on fern fronds that are twicepinnate, the leaf first being divided into pinnae, then the pinnae into pinnules

Disease

(L. dis, a prefix signifying the opposite + M.E. aise, comfort, literally the opposite of ease) any alteration from a state of metabolism necessary for the normal development and functioning of an organism

Dominant

(L. dominari, to rule) in ecology, referring to species of a community that receive the full force of the macroenvironment; usually the most abundant of such species, and not all of them; in heredity, referring to that allele that, when present in a hybrid with a contrasting allele, completely controls the development of the character; in peas, tall is dominant over dwarf

Dormant

(L. dormire, to sleep) being in a state of reduced physiologic activity such as occurs in seeds, buds, and so on

Drupe

(L. drupa, an overripe olive) a simple, fleshy fruit, derived from a single carpel, usually one-seeded, in which the exocarp is thin, the mesocarp fleshy, and the endocarp stony

Erosion

(L. e, put + rodere, to gnaw) the wearing away of land, generally by the action of water

Electronegativity

(L. electrum, amber + negativity) the power of an atom to attract electrons

Element

(L. elementa, the first principles; according to one system of medieval chemistry as recent as 1700, there were four elements composing all material bodies: earth, water, air, and fire) in modern chemistry, a substance that cannot be divided by any known chemical means to a simpler substance; a substance formed entirely from atoms of a distinctive atomic number (number of protons)

Enation

(L. enasci, to issue forth) a leaf that originates as an epidermal outgrowth, and thus is not associated with a vascular trace and vascular gap

Eukarya

(L. eu, true + karyon, a nut, referring in modern biology to the nucleus) a taxonomic domain of organisms characterized by having cellular organelles, specifically including the nucleus, bounded by membranes

Evolution

(L. evolutio, an unrolling) in biology, any change in hereditary characteristics of a population or species, or the formation of new species

Family

(L. familia, family) in the taxonomic hierarchy, a group of genera

Fascicle

(L. fasciculus, a small bundle) a bundle of pine or other needle-leaves of gymnosperms

Fermentation

(L. fermentum, a drink made from fermented barley beer) a catabolic process in which molecular oxygen is not involved, such as the production of alcohol from sugar by yeasts

Fertilization

(L. fertilis, capable of producing fruit) that state of a sexual life cycle involving the union of egg and sperm and, hence, the doubling of chromosome numbers

Filament

(L. fi'lum, a thread) stalk of stamen bearing the anther at its tip; also, a slender row of cells (certain algae)

Fiber

(L. fibea, a fiber or filament) an elongated, tapering, thick-walled strengthening cell occurring in various parts of plant bodies; one of the cell types in sclerenchyma tissue

Fission

(L. fissilis, easily split) asexual reproduction involving the division of a single-celled individual into two new single-celled individuals of equal size

Flagellum (plural, flagella)

(L. flagellum, a whip) a long, slender whip of protoplasm (in eukaryotes) or proteins (in bacteria)

Flora

(L. floris, a flower) an enumeration of all the species that grow in a region; also, the collective term for all the species that grow in a region

Foliose

(L. folium, a leaf) said of a lichen that is leaflike, attached to the substrate only along part of its surface

Follicle

(L. folliculus, dim. of follis, bag) a simple, dry, dehiscent fruit, with one carpel, splitting along one suture

Foraminifera

(L. foramen, an opening) nonphotosynthetic, aquatic, unicellular protists that have a calcareous shell with perforations through which filaments of protoplasm (pseudopods) project, capable of trapping or engulfing food; classified within the alveolates

Forest

(L. foris, outside) vegetation dominated by trees, in which the canopies of adjacent trees usually touch, providing more than 60% cover

Fossil

(L. fossio, a digging) any impression, natural or impregnated remains, or other trace of an animal or plant of past geologic ages that has been preserved in the earth's crust

Frequency

(L. frequens, crowded) the percentage of vegetation samples containing a given species; if 7 of 10 quadrats (samples) contained post oaks, post oak has a 70% frequency

Frond

(L. frons, branch, leaf) a synonym for a large divided leaf, especially a fern leaf; also the leaflike blades of some algae

Fruit

(L. fructus, that which is enjoyed, hence product of the soil, trees, cattle, and so on) a matured ovary; in some, seed plants and other parts of the flower may be included; also applied, as fruiting body, to reproductive structures of other groups of plants

Frustule

(L. frustulum, little piece) a diatom cell, composed of two overlapping halves (valves)

Fruticose

(L. frutex, a shrub) said of a lichen that is highly branched and erect or pendant

Fungus (plural, fungi)

(L. fungus, a mushroom) any chemoheterotrophic eukaryote that reproduces with spores and has cell walls at some stage of life

Funiculus

(L. funiculus, dim. of funis, rope or small cord) a stalk of the ovule, containing vascular tissue

Fusiform initials

(L. fusus, spindle + form) meristematic cells in the vascular cambium that develop into secondary xylem and phloem cells composing the axial system of a stem or root

Gel

(L. gelare, to freeze) jelly-like, colloidal mass

Gemma (plural, gemmae)

(L. gemma, a bud) a small mass of vegetative tissue; an outgrowth of the thallus

Generation

(L. genus, birth, race, kind) any phase of a life cycle characterized by a particular chromosome number, as the gametophyte generation and the sporophyte generation

Germination

(L. germinare, to sprout) the beginning or resumption of growth by a seed, spore, bud, or other resting structure

Grana (singular, granum)

(L. granurn, a seed) dense collections of thylakoid membranes within chloroplasts, seen as green granules with the light microscope and as a series of apposed lamellae with the electron microscope

Gravitropism

(L. gravis, heavy + Gr. tropos, turning) a growth curvature induced by gravity

Guttation

(L. gutta, drop, exudation of drops) exudation of water from plants, in liquid form

Habitat

(L. habitare, inhabit, dwell) the place or natural environment where an organism naturally grows

Hallucinogenic

(L. hallucinari, to mentally wander + genitalis, to beget) that which induces hallucinations

Herbicide

(L. herba, grass or herb + cidere, to kill) a chemical used to kill plants, frequently chemically related to a hormone (as the herbicide 2,4-D is related to the hormone IAA); an herbicide may have narrow or wide selectivity (range of target organisms)

Herbal

(L. herba, grass) a book that contains the names and descriptions of plants, especially those that are thought to have medicinal uses

Herbarium

(L. herba, grass) a collection of dried and pressed plant specimens

Herb

(L. herba, grass, green blades) a seed plant that does not develop woody tissues

Herbaceous

(L. herbaceus, grassy) referring to plants having the characteristics of herbs

Heredity

(L. hereditas, being an heir) the transmission of morphologic and physiologic characters of parents to their offspring

Hilum

(L. hilum, a trifle) scar on a seed, which marks the place where the seed broke from the stalk

Host

(L. hospes, host, guest) an organism on or in which another organism lives

Humidity, relative

(L. humidus, moist) the ratio of the weight of water vapor in a given quantity of air to the total weight of water vapor that quantity of air is capable of holding at the temperature in question, expressed as a percentage

Humus

(L. humus, the ground) decomposing organic matter in the soil

Hybrid

(L. hybrida, offspring of a tame sow and a wild boar, a mongrel) in taxonomy, an organism that results from a mating between organisms of different species; in genetics, the offspring of any mating between organisms that carry different alleles for a gene of interest

Hypantheum

(L. hypo, under + Gr. anthos, flower) fusion of calyx and corolla partway up their length to form a cup, as in many members of the rose family

Imbibition

(L. imbibere, to drink) the absorption of water by a seed, an adsorption phenomenon

Environment

(L. in + viron, circle) the totality of biotic and abiotic factors that affect an organism

Indehiscent

(L. in, not + dehiscere, to divide) not opening by valves or along regular lines

Indusium (plural, indusia)

(L. indusium, a woman's undergarment) membranous growth of the epidermis of a fern leaf that covers a sorus

Infect

(L. infectus, to put into, to taint with morbid matter) specifically, to produce disease by such agents as bacteria or viruses

Inflorescence

(L. inflorescere, to begin to bloom) a flower cluster

Integument

(L. integumentum, covering) external layer of ovule that later develops into the seed coat

Interphase

(L. inter, between + Gr. phasis, appearance) the period of preparation for cell division; state between two mitotic or meiotic cycles

Intercellular

(L. inter, between + cells) lying between cells

Interfascicular cambium

(L. inter, between + fasciculus, small bundle) cambium that develops between vascular bundles

Internode

(L. inter, between + nodus, a knot) the region of a stem between two successive nodes

Intermediate

(L. inter-, between + medius, middle) a compound in a metabolic pathway that occurs before the final product

Intercalary

(L. intercalare, to insert) descriptive of meristematic tissue or growth not restricted to the apex of an organ, that is, growth at nodes

Intracellular

(L. intra, within + cell) lying within cells

Introgression

(L. intro, to the inside + gress, walk) transfer of genes between two species by means of hybridization followed by back-crossing

Iteroparous

(L. iterum, again + paritas, equal) a perennial plant capable of flowering repeatedly throughout its life span

Middle lamella

(L. lamella, a thin plate or scale) original thin membrane separating two adjacent protoplasts and remaining as a distinct cementing layer between adjacent cell walls

Lamina

(L. lamina, a thin plate) blade or expanded part of a leaf

Legume

(L. legumen, any leguminous plant, particularly bean) a simple, dry dehiscent fruit with one carpel, splitting along two sutures

Lignification

(L. lignum, wood + facere, to make) impregnation of a cell wall with lignin

Lignin

(L. lignum, wood) an irregular polymer of phenolic molecules impregnating the cellulose framework of certain plant cell walls; adds strength and reduces extensibility of the cell walls

Ligule

(L. ligula, dim. of lingua, tongue) in grass leaves, an outgrowth from the upper and inner side of the leaf blade where it joins the sheath

Lumen

(L. lumen, light, an opening for light) the cavity of the cell within the cell walls

Medulla

(L. medulla, marrow) the filamentous center of certain lichens and kelp blades and stipes

Membrane

(L. membrana, skin, parchment) generally, a thin, soft, pliable sheet; specifically, a limiting surface, within or surrounding a cell, formed from phospholipids, glycolipids, or other hydrophobic compounds

Mollisol

(L. mollis, soft + solum, soil, solid) one of the 11 world soil orders, characterized by containing more than 1% organic matter in the top 17.5 cm and associated with grassland vegetation; synonymous with chernozem

Multiciliate

(L. multus, many + F. cil, an eyelash) having many cilia present on a sperm or spore or other type of ciliated cell

Moss

(L. muscus, moss; M.E., O.E. mos, moss) one lineage of bryophytes, having gametophytes with leaflike, stemlike, and rootlike organs, and producing sporophytes that grow on and up above the gametophyte, with a stalk and a capsule containing spores

Mutation

(L. mutare, to change) a heritable trait appearing in an individual as the result of a change in DNA sequence or chromosome structure

Mutant

(L. mutare, to change) an individual containing a gene that differs from those of its parents

Mutualism

(L. mutuus, reciprocal) a symbiotic relationship between two organisms that benefits both organisms

Neutron

(L. neuter, neither) an uncharged particle found in the atomic nucleus of all elements except hydrogen; the helium nucleus has two protons and two neutrons; mass of a neutron is equal to 1.67 x 10-24 g

Nitrification

(L. nitrum, nitro, a combining form indicating the presence of nitrogen + facere, to make) change of ammonium salts into nitrates through the activities of certain bacteria

Nodule

(L. nodulus dim. of nodus, a knot) knot or swelling on a root, especially one containing nitrogen-fixing bacteria

Node

(L. nodus, a knot) in plant anatomy, a point on a stem where a leaf and axillary bud occur, and where branches originate; in cladistics, a branch point in a cladogram where one species divides into two new species (speciation)

Nucellus

(L. nucella, a small nut) tissue composing the chief part of the young ovule, in which the embryo sac develops; megasporangium

Nucleolus (plural, nucleoli)

(L. nucleolus, a small nucleus) dense body in the nucleus; site of ribosome synthesis

Nucleus (plural, nuclei)

(L. nucleus, kernel of a nut) in biology, an organelle characteristic of eukaryotes, containing DNA within an evelope made of two concentric membranes; in chemistry, the positively charged central part of an atom carrying most of the atom's mass

Nut

(L. nux, nut) a dry, indehiscent, hard, one-seeded fruit, generally produced from a compound ovary

Operculum

(L. operculum, a lid) in mosses, cap of sporangium

Order

(L. ordo, a row of threads in a loom) in the taxonomic hierarchy, a group of families

Organ

(L. organum, an instrument or engine of any kind, musical, military, and so on) a part or member of an animal or plant body or cell adapted by its structure for a particular function

Ovary

(L. ovum, an egg) enlarged basal portion of the pistil, which becomes the fruit

Palmately veined

(L. paama, palm of the hand) descriptive of a leaf blade with several principal veins spreading out from the upper end of the petiole

Panicle

(L. panicula, a tuft) an inflorescence, the main axis of which is branched, and whose branches bear loose racemose flower clusters

Pappus

(L. pappus, woolly, hairy seed or fruit of certain plants) scales or bristles representing a reduced calyx in composite flowers

Pedicel

(L. pediculus, a little foot) stalk or stem of the individual flowers of an inflorescence

Peduncle

(L. pedunculus, a late form of pediculus, a little foot) stalk or stem of a flower that is borne singly; or the main stem of an inflorescence

Perennial

(L. perennis, lasting the whole year through) a plant that lives more than 2 years

Permafrost

(L. permanere, to remain + A.S. freosan, to freeze) soil that is permanently frozen; usually found some distance below a surface layer that thaws during warm weather

Permeable

(L. permeabilis, that which can be penetrated) said of a membrane, cell, or cell system through which substances may diffuse

Petiole

(L. petiolus, a little foot or leg) stalk of leaf

Pilus

(L. pilus, hair) a structure on the surface of a bacterial cell resembling a hair

Pigment

(L. pingere, to paint) a substance that absorbs visible light; hence, appears colored

Pinnately veined

(L. pinna, a feather + vena, a vein) descriptive of a leaf blade with single midrib from which smaller veins branch off, somewhat like the divisions of a feather

Pistil

(L. pistillum, a pestle) central organ of the flower, typically consisting of ovary, style, and stigma

Placentation

(L. placenta, a cake + tion, state of) manner in which the placentae are distributed in the ovary

Placenta (plural, placentae)

(L. placenta, a cake) the tissue within the ovary to which the ovules are attached

Plant geography

(L. planta, shoot + Gr. ge, Earth + graphein, to write) a synonym for biogeography; the study of the geographic distribution of plants, often including distributions in geologic time, as well as in the present, and with a focus on taxonomically related plant groups (families, genera)

Plumule

(L. plumula, a small feather) the first bud of an embryo or that portion of the young shoot above the cotyledons

Pollen, pollen grain

(L. pollen, fine flour) the immature male gametophytes of seed plants

Pollinium

(L. pollentis, powerful or pollinis, fine flour + ium, group) a mass of pollen that sticks together and is transported by pollinators as a mass; present in orchids and milkweeds

Pome

(L. pomum, apple) a simple, fleshy fruit, the outer portion of which is formed by the floral parts that surround the ovary

Population

(L. populus, people) a group of closely related, interbreeding organisms

Prairie

(L. pratum, meadow) grassland vegetation, with trees essentially absent; often considered to have more rainfall than does the steppe

Predation

(L. predatio, plundering) a form of biological interaction in which one organism is destroyed (by ingestion); parasitism, carnivory, and seed herbivory are forms of predation

Leaf primordium

(L. primordium, a beginning) a lateral outgrowth from the apical meristem, which will become a leaf

Primordium

(L. primus, first + ordiri, to begin to weave; literally beginning to weave, or to put things in order) the beginning or origin of any part of an organ

Primary

(L. primus, first) first in order of time or development

Procambium

(L. pro, before + cambium) a primary meristem that gives rise to primary vascular tissues and, in most woody plants, to the vascular cambium

Proembryo

(L. pro, before + embryon, embryo) a group of cells arising from the division of the fertilized egg cell before those cells that are to become the embryo are recognizable

Producer

(L. producere, to draw forward) an organism that produces organic matter for itself and other organisms (consumers and decomposers) by photosynthesis

Quadrat

(L. quadrus, a square) a frame of any shape that, when placed over vegetation, defines a unit sample area within which the plants may be counted or measured

Cork

(L. quercus, oak) an external, secondary tissue impermeable to water and gases

Quiescent center

(L. quiescere, to rest) disk-shaped region of root apex containing slowly dividing cells

Raceme

(L. racemus, a bunch of grapes) an inflorescence in which the main axis is elongated but the flowers are born on pedicels that are about equal in length

Ray initials

(L. radius, a beam or ray) meristematic cells in the vascular cambium that develop into xylem and phloem cells composing the ray system

Radicle

(L. radix, root) portion of the plant embryo that develops into the primary root

Recombination

(L. re, repeatedly + combinatus, joined) a rearrangement of the collection of alleles of different genes through independent segregation or crossingover, so that the genotype of a meiotic product (that is, gamete, meiospore) of an individual differs from those of its parents

Reproduction

(L. re, repeatedly + producere, to give birth to) the process by which plants and animals give rise to offspring

Respiration

(L. re, repeatedly + spirare, to breathe) a chemical oxidation controlled and catalyzed by enzymes that break down carbohydrate and fats, thus releasing energy to be used by the organism in doing work

Receptacle

(L. receptaculum, a reservoir) enlarged end of the pedicel or peduncle to which other flower parts are attached

Resin duct

(L. resina, resin + ductus, led) resin canal; in conifers, continuous tubes lined with secretory cells that run through the sap-wood; they function as repositories for metabolic byproducts

Resin

(L. resina, resin) a viscose, sticky fluid of plant origin, used by woody plants to repel wood-burrowing insect pests; humans collect resin as copal, rosin, or amber, and they use resin in the manufacture of various lacquers, varnishes, inks, adhesives, and plastics

Restoration

(L. restaure, brought back) in ecology, the process of modifying the environment and the vegetation of an ecosystem that has been degraded by human- caused disturbances and stresses to return that ecosystem to its predisturbed state

Reticulum

(L. reticulum, a small net) a small net

Samara

(L. samara, the fruit of the elm) simple, dry, one- or two-seeded indehiscent fruit with pericarp bearing a winglike outgrowth

Scalariform vessel

(L. scala, ladder + form) a vessel with secondary thickening resembling a ladder

Scutellum

(L. scutella, a dim. of scutum, shield) single cotyledon of grass embryo

Senescence

(L. senescere, to grow old) the phase of plant growth that extends from full maturity to death and is characterized by a breakdown of functional cellular components, accumulation of metabolic products, and (often) an increase in respiratory rate and synthesis of ethylene

Septicidal dehiscence

(L. septum, fence + caedere, to cut; dehiscere, to split open) the splitting open of a capsule along the line of union of carpels

Septum

(L. septum, fence) any dividing wall or partition; frequently, a cross wall in a fungal or algal filament

Septate

(L. septum, fence) divided by cross walls into cells or compartments

Serpentine

(L. serpens, a serpent) referring to soil derived from metamorphic parent material characterized, among other things, by low calcium (Ca), high magnesium (Mg), and a greenish-gray color

Seta (plural, setae)

(L. seta, a bristle) in bryophytes, a short stalk of the sporophyte, which connects the foot and the capsule

Silique

(L. siliqua, pod) the fruit characteristic of Brassicaceae (mustards); two-celled, the valves splitting from the bottom and leaving the placentae with the false partition stretched between

Soil

(L. solum, soil, solid) the uppermost stratum of the earth's crust, which has been modified by weathering and organic activity into (typically) three horizons: an upper A horizon that is leached, a middle B horizon in which the leached material accumulates, and a lower C horizon, which is unweathered parent material

Solute

(L. solutus, from solvere, to loosen) a dissolved substance

Solvent

(L. solvere, to loosen) a substance, usually a liquid, having the properties of dissolving other substances

Species

(L. species, appearance, form, kind) a group of organisms that are more closely related to one another than to organisms of any other kind; members of a given species may also look more like one another and interbreed more freely with one another than with organisms outside the group

Spikelet

(L. spica, an ear of grain + let, dim. ending), the unit of inflorescence in grasses; a small group of grass flowers

Spike

(L. spica, an ear of grain) an inflorescence in which the main axis is elongated and the flowers are sessile

Spirillum

(L. spira, a coil) a bacterial cell that has a spiral shape

Stamen

(L. stamen, the standing-up things or a tuft of thready things) flower structure made up of an anther (pollen-bearing portion) and a stalk or filament

Stigma

(L. stigma, a prick, a spot, a mark) receptive portion of the style to which pollen adheres

Stipe

(L. stipes, post, tree trunk) the stalk portion of a kelp or a mushroom

Stipule

(L. stipula, dim. of stipes, a stock or trunk) a leaflike structure from either side of the leaf base

Stolon

(L. stolo, a shoot) a stem that grows horizontally along the ground surface

Suberin

(L. suber, the cork oak) a waxy material found in the cell walls of cork tissue

Succession

(L. successio, a coming into the place of another) a sequence of changes in time of the species that inhabit an area, from an initial pioneer community to a final climax community

Succulent

(L. sucus, juice) a plant having juicy or watery tissues

Suspensor

(L. suspendere, to hang) a cell or chain of cells developed from a zygote, the function of which is to place the embryo cells in an advantageous position to receive food

Tendril

(L. tendere, to stretch out, to extend) a slender coiling organ that aids in the support of stems

Testa

(L. testa, brick, shell) the outer coat of the seed

Totipotent

(L. totus, whole + patens, being able) capable of development along any of the lines inherently possible to cells of its species

Toxin

(L. toxicum, poison) a poisonous secretion of a plant or animal

Translocation

(L. trans, across + locare, to place) the transfer of food materials or products of metabolism; in genetics, the exchange of chromosome segments between nonhomologous chromosomes

Transcription

(L. trans, across + scribere, to write) the process of RNA formation from a DNA code

Tuber

(L. tuber, a bump, swelling) a much-enlarged, short, fleshy underground stem

Turgid

(L. turgidus, swollen, inflated) swollen, distended; referring to a cell that is firm because of water uptake

Turgor pressure

(L. turgor, a swelling) the pressure within a cell resulting from the osmotically generated imbibition of water into the protoplasm and vacuole

Umbel

(L. umbella, a sunshade) an inflorescence, the individual pedicles of which all arise from the apex of the peduncle

Uniseriate

(L. unus, one + M.L. seriatus, to arrange in a series) said of a filament having a single row of cells

Unicell

(L. unus, one + cell) an organism consisting of a single cell; generally used in describing algae

Uredospore

(L. uredo, a blight + spore) a red, one-celled summer spore in the life cycle of the rust fungi

Vascular

(L. vasculum, a small vessel) referring to a plant tissue (xylem and phloem) or region consisting of or giving rise to conducting tissue; for example, vascular bundle, vascular cambium, phloem ray

Vessel

(L. vasculum, a small vessel) tube of determinate length composed of vessel members joined end to end by opened perforation plates; the end wall of the terminal vessel member of a vessel are closed

Shoot

(derivation uncertain, but early referring to new plant growth) a young branch that shoots out from the main stock of a tree, or the young main portion of a plant growing aboveground

Fibril

(dim. of L. fibea, fiber) submicroscopic threadlike units of cellulose found in cell walls

Rosette

(dim. of L. rose, rose) a shoot with a very short stem, composed of several unelongated internodes but with fully expanded leaves

Gametophyte

(gamete + Gr. phyton, a plant) the gameteproducing plant

Genome

(gene + chromosome) the collection of all genes in an organism

Genotype

(gene + type) the assemblage of genes in an organism

Ethylene

C2H4, a plant hormone regulating fruit ripening, various aspects of vegetative growth, and the abscission process

Egg

(A.S. aeg, egg) a female gamete; in plants, one of eight cells in an embryo sac

Fat

(A.S. faett, fatted) one of the three major types of foods (the other two are carbohydrates and proteins); nonpolar, containing carbon, hydrogen, and small amounts of oxygen; rich in energy; used synonymously with lipids

Food

(A.S. foda) any organic substance that directly furnishes energy and building materials for vital processes

Growth

(A.S. growan, probably from Old Teutonic gro, from which grass also is derived) increasing the size and number of cells in an organ; has two components: cell division and cell enlargement

Ripening

(A.S. rifi, perhaps related to reap) changes in a fruit that follow seed maturation and that prepare the fruit for its function of seed dispersal

Root

(A.S. rot) in plant anatomy, a usually underground organ adapted for growth through soil and absorption of minerals and water, containing a central vascular cylinder; in cladistics, the oldest node in a clade or cladogram

Scrub

(A.S. scrob, a shrub) vegetation dominated by shrubs; described as thorn forest in areas with moderate rainfall, or as chaparral or desert in areas with low rainfall

Seed

(A.S. sed, anything that may be sown) popularly, as originally used, anything that may be sown; that is, "seed" potatoes, "seeds" of corn, sunflower, and so on; botanically, a seed is the matured ovule without accessory parts

Spindle

(A.S. spinel, an instrument used in spinning thread by hand) referring in mitosis and meiosis to the spindle-shaped intracellular structure in which the chromosomes move

Weed

(A.S. weod, used at least since 888 in its present meaning) generally a herbaceous plant or shrub not valued for use or beauty, growing where unwanted, and regarded as using ground or hindering the growth of more desirable plants

Ammonification

(Ammon, Egyptian sun god, near whose temple ammonium salts were first prepared from camel dung + L. facere, to make) decomposition of amino acids, resulting in the production of ammonia

Alkali

(Arabic alqili, the ashes of the plant saltwort) a substance with marked basic properties

Acid

(F. acide, from L. acidus, sharp) a substance that can donate a hydrogen ion; most typical acids are sour and are compounds of hydrogen with another element or elements

Action spectrum

(F. acte, a thing done) a graph relating the degree of physiologic response (for example, phototropism, photosynthesis) caused by different wavelengths of light

Anaphase

(Gr. ana, up + phais, appearance) that stage in mitosis in which half chromosomes or sister chromatids move to opposite poles of the cell

Anatomy

(Gr. anatome, dissection), the study of the internal structure of organisms

Androecium

(Gr. andros, man + oikos, house) the aggregate of stamens in the flower of a seed plant

Aneuploid

(Gr. aneu, without + ploid) the condition in which the number of chromosomes differs from the normal by less than a full set (n), for example, 3n + 1, 2n - 1, 2n + 4; compare Polyploid

Angiosperm

(Gr. angion, a vessel + sperma from speirein, to sow, hence a seed or germ) literally a seed borne in a vessel, thus a group of plants whose seeds are borne within a matured ovary

Anthocyanin

(Gr. anthros, a flower + kyanos, dark blue) a blue, purple, or red vacuolar pigment

Antibody

(Gr. anti, against + body) a protein produced in an organism, in response by the organism to a contact with a foreign substance, and having the ability of specifically reacting with the foreign substance

Anticlinal cell division

(Gr. anti, against + klinein, incline) cell division where the newly formed cell wall is perpendicular to the axis of the organ surface

Chromosome

(Gr. chroma, color + soma, body) a nuclear body containing genes in a linear order and undergoing characteristic division stages; one of the units of condensed chromatin visible during cell division

Chromatin

(Gr. chroma, color) substance in the nucleus that readily takes artificial staining; a complex of DNA and proteins

Chromatophores

(Gr. chromo, color + phorus, a bearer) in algae, bodies bearing chlorophyll; in bacteria, small bodies, about 100 nm in diameter, containing chlorophyll, protein, and a carbohydrate

Chemotropism

(Gr. chymeia, to pour + Gr. tropos, a turning) an orientation of growth in response to a chemical agent; the organ usually grows toward or away from the source of the chemical

Chemotroph

(Gr. chymeia, to pour, later alchemy, chemistry + trophein, to feed) bacteria that oxidize reduced inorganic compounds such as H2S to obtain energy

Plant demography

(Gr. demos, people + graphein, to write) demography was originally the study of births, deaths, density, and distribution of human populations; plant demography is this study applied to plant populations

Dikaryotic mycelium

(Gr. di, two + karyon, nut) a mycelium that has paired haploid nuclei of different genotypes in each septate compartment; also called a dikaryon

Diatomite

(Gr. diatomos, cut in two) fossil deposits of diatom cell walls; currently mined for such commercial purposes as filters, extenders, and stabilizers

Diatom

(Gr. diatomos, cut in two) member of a group of golden brown algae with silicious cell walls fitting together much as do the halves of a pill box

Dichotomy

(Gr. dicha, in two) the forking of an axis into two branches

Dictyosome

(Gr. diktyon, a net + some, body) one of the component parts of the Golgi apparatus; in plant cells, a complex of flattened double lamellae

Dinoflagellates

(Gr. dinein, to whorl + L. flagellum, a whip) unicellular algae with two unequal lateral flagella; prominent in marine phytoplankton and capable of causing red tides; classified in the alveolate clade in this text

Diploid

(Gr. diploos, double + oides, like) having a double set of chromosomes, or referring to an individual containing a double set of chromosomes per cell; usually a sporophyte generation

Dihybrid cross

(Gr. dis, twice + hybrida, the offspring of a tame sow and a wild boar, a mongrel) a cross between organisms differing in two characters

Dicots

(Gr. dis, twice + kotyledon, a cup-shaped hollow) formally, dicotyledonous plants: plants with embryos having two cotyledons; current systematics now breaks up this group into eudicots, magnoliids, and a few basal angiosperms

Dioecious

(Gr. dis, twice + oikos, house) unisexual; having the male and female elements in different individuals

Ectomycorrhiza

(Gr. ektos, outside + mykos, fungus + riza, root) a mycorrhiza in which fungal hyphae coat the outside of root tips and grow between root cells but do not penetrate through root cell walls

Electrophoresis

(Gr. elektron, amber + phora, motion + esis, drive) the process of causing charged molecules (for example, proteins) to move between positively and negatively charged poles

Electron

(Gr. elektron, gleaming in the sun, by way of L. electrum, a bright alloy of gold and silver, and finally amber, from which the first electricity was produced by friction) an elementary particle of matter bearing a unit of negative electrical charge; low in mass, electrons surround the atom's positively charged nucleus; their arrangement defines the size and chemical properties of the atom or molecule

Embryo

(Gr. en, in + bryein, to swell) a young sporophytic plant, while still retained in the gametophyte or in the seed

Heteroecious

(Gr. heteros, different + oikos, house) referring to fungi that cannot carry through their complete life cycle unless two different host species are present

Heterosis

(Gr. heteros, different + osis, suffix indicating a state of) the state of a genotype having a large degree of heterozygosity

Heterospory

(Gr. heteros, different + spore) the condition of producing microspores and megaspores

Heterotrophic

(Gr. heteros, different + trophein, to nourish with food) referring to a prokaryote that obtains carbon from the breakdown of organic molecules, and more generally, to an organism that requires organic compounds it cannot make for itself and, hence, must get from the environment

Heterozygous

(Gr. heteros, different + zygon, yoke) having different allels of a Mendelian gene pair present in the same cell or organism; for instance, a tall pea plant with alleles for tallness, T, and dwarfness, t

Hybrid vigor (heterosis)

(Gr. heterosis, alteration fr. heteros, other) a greater capacity for growth frequently observed in crossbred animals or plants as compared with those resulting from inbreeding

Hexose

(Gr. hexa, six + ose, suffix indicating, in this usage, carbohydrate) a carbohydrate with six carbon atoms

Homologous chromosomes

(Gr. homologos, the same) members of a chromosome pair; they may be heterozygous or homozygous

Homospory

(Gr. homos, one and the same + spore) the condition of producing one sort of spore only

Homozygous

(Gr. homos, one and the same + zygon, yoke) having identical alleles of a Mendelian gene pair present in the same cell or organism; for instance, a tall pea plant with alleles for tallness (TT) only

Whorl

a circle of flower parts, or of leaves

Core angiosperms

a clade containing the most flowering plants; can be subdivided into the subclades magnoliids, monocots, and eudicots

Commelinids

a clade of monocots typically having nonshowy flowers; palms, grasses, sedges, bromeliads, ginger, banana, and the bird-of-paradise are examples

Heterokonts

a clade of protists that includes several algal groups with chlorophylls a and c (golden algae, brown algae, diatoms) and the oomycota (water molds, downy mildews)

Rooted cladogram

a cladogram in which the earliest or root node of the clade of interest is identified, thereby establishing the sequence of evolutionary events throughout the cladogram

Unrooted cladogram

a cladogram that does not identify the earliest node in the clade (the root), and therefore does not specify the direction of evolution between internal nodes of the cladogram

Aflatoxin

a class of cancer-causing compounds produced by the fungus Aspergillus flavus and deposited in infected nuts and grains

Sterols

a class of lipids, including (in animals) cholesterol and (in plants) ergosterol, often contributing to the structure of biological membranes

Multiple fruit

a cluster of matured ovaries produced by separate flowers; for example, a pineapple

Nicotinamide adenine dinucleotide phosphate (NADPH)

a coenzyme capable of being reduced

Nicotinamide adenine dinucleotide (NADH)

a coenzyme capable of being reduced (accepting electrons)

Hormone

(Gr. hormaein, to excite) a specific organic product, produced in one part of a plant or animal body and transported to another part where, effective in small amounts, it controls or stimulates another and different process

Hornworts

(Gr. horn, horn + wort, plant) a group of bryophytes with long, pointed sporophytes (resembling horns) that rise from the thalloid gametophytes

Hydathode

(Gr. hydro, water + O.E. thoden, stem or thyddan, to thrust) a structure, usually on leaves, that releases liquid water during guttation

Hydroid

(Gr. hydro, water + eidos, a shape) a waterconducting cell found in some mosses

Hydrolysis

(Gr. hydro, water + lysis, loosening) the breaking of a covalent bond within a compound through reaction with water; in metabolism, generally controlled by enzymes

Hydrophilic

(Gr. hydro, water + philos, loving) soluble in water, capable of forming weak associations with water molecules

Hydrophobic

(Gr. hydro, water + phobos, fearing) insoluble in water

Hydrophyte

(Gr. hydro, water + phyton, a plant) a plant that grows wholly or partly submerged in water

Hymenium

(Gr. hymen, a membrane) spore-bearing tissue in various fungi

Hypha (plural, hyphae)

(Gr. hypee, a web) a tubular, threadlike eukaryotic cell (or portion of a cell) that bears one or more nuclei and grows at the tip, characteristic of fungi

Hypertonic

(Gr. hyper, above, over + tonos, to stretch) a solution having a concentration high enough so that water will move into it across a membrane from another solution

Hypogeal

(Gr. hypo, under + ge, the earth) type of germination where cotyledons remain belowground

Hypogyny

(Gr. hypo, under + gyne, female) a condition in which the receptacle is convex or conical, and the flower parts are situated one above another in the following order, beginning with the lowest: sepals, petals, stamens, carpels

Hypocotyl

(Gr. hypo, under + kotyledon, a cup-shaped hollow) that portion of an embryo or seedling between the cotyledons and the radicle or young root

Hypolimnion

(Gr. hypo, under + limne, marsh) a lower, cold, relatively nonaerated zone of water that lies below a warmer zone (the epilimnion); common in large bodies of freshwater, such as deep lakes

Hypothesis

(Gr. hypothesis, foundation) a tentative theory or supposition provisionally adopted to explain certain facts and to guide in the investigation of other facts

Ion

(Gr. ienai, to go) a charged particle formed by the breakdown of substances able to conduct an electric current

Isomorphic

(Gr. iso, equal + morphe, form) referring to organisms with sporic life cycles in which the sporophyte and gametophyte generations look the same

Isomers

(Gr. isos, equal + meros, part) two or more compounds having the same molecular formula; for example, glucose and fructose are both C6H12O6

Isotonic

(Gr. isos, equal + tonos, to stretch) having equal osmotic concentration

Isotope

(Gr. isos, equal + topos, place) any of two or more forms of an element having the same or closely related chemical properties

Cenozoic

(Gr. kainos, recent + zoe, life) the geologic era extending from 65 million years ago to the present

Calyptra

(Gr. kalyptra, a veil, covering) in bryophytes, an envelope covering the developing sporophyte, formed by growth of the venter of the archegonium

Calyx

(Gr. kalyx, a husk, cup) sepals collectively; outermost flower whorl

Canopy

(Gr. kanopeion, a cover over a bed to keep off gnats) the leafy portion of a tree or shrub

Carpel

(Gr. karpos, fruit) a floral leaf bearing ovules along the margins

Caryopsis

(Gr. karyon, a nut + opsis, appearance) a simple, dry, one-seeded, indehiscent fruit, with pericarp firmly united all around to the seed coat; also called a grain

Karyogamy

(Gr. karyon, nut + gamos, marriage) the fusion of two nuclei

Cation exchange

(Gr. kata, downward) the replacement of one positive ion (cation) by another, as on a negatively charged clay particle

Catalyst

(Gr. katelyein, to dissolve) a substance that accelerates a chemical reaction but that is not used up in the reaction

Macroenvironment

(Gr. makros, large + O.F. environ, about) the environment caused by the general, regional climate; traditionally measured some 4 feet above the ground and away from large obstructions

Megafossil

(Gr. megas, great + L. fossilis, dug up) a fossil large enough to be seen without magnification; leaves, flowers, stems, and seeds are examples

Megaphyll

(Gr. megas, great + phyllon, leaf) a leaf whose trace is marked with a gap in the stem's vascular system; megaphylls are thought to represent modified branch systems

Megasporocyte

(Gr. megas, large + spora, seed + L. cyta, vessel) a diploid cell in which meiosis will occur, resulting in four megaspores; synonymous with megaspore mother cell

Megasporangium

(Gr. megas, large + sporangium) sporangium that bears megaspores

Megasporophyll

(Gr. megas, large + spore + Gr. phyllon, leaf) a leaf bearing one or more megasporangium

Megaspore

(Gr. megas, large + spore) the meiospore of vascular plants, which gives rise to a female gametophyte

Meiosis

(Gr. meioun, to make smaller) a type of cell division occurring in sexual reproduction, in which two rounds of division convert one diploid cell to four haploid cells, effecting a segregation of homologous chromosomes

Ground meristem

(Gr. meristos, divisible) a primary meristem that gives rise to cortex, mesophyll, and pith

Meristem

(Gr. meristos, divisible) sites in the plant body where cells divide and where differentiation into specialized cells and tissues is initiated

Mesocarp

(Gr. mesos, middle + karpos, fruit) middle layer of fruit wall (pericarp)

Mesophyll

(Gr. mesos, middle + phyllon, leaf) parenchyma tissue of leaf between epidermal layers, where most photosynthesis takes place

Mesophyte

(Gr. mesos, middle + phyton, a plant) a plant that grows best in conditions of moderate moisture and temperature

Mesosome

(Gr. mesos, middle + soma, body) one of a series of paired membranes occurring in many bacteria

Mesozoic era

(Gr. mesos, middle + zoe, life) a geologic era beginning 225 million years ago and ending 65 million years ago

Metaphase

(Gr. meta, after + phasis, appearance) stage of mitosis during which the chromosomes, or at least the kinetochores, lie in the central plane of the spindle

Metaxylem

(Gr. meta, after + xylon, wood) last formed primary xylem

Microsporangium (plural, microsporangia)

(Gr. mikros, little + sporangium) a sporangium that bears microspores

Microsporophyll

(Gr. mikros, little + spore + Gr. phyllon, leaf) a leaf bearing microsporangia

Microenvironment

(Gr. mikros, small + O.F. environ, about) the environment close enough to the surface of a living or nonliving object to be influenced by it

Microfibrils

(Gr. mikros, small + fibrils, dim. of fiber; literally, small little fibers) the translation of the name expresses the concept very well; microfibrils are exceedingly small fibers visible only with the high magnifications of the electron microscope

Microphyll

(Gr. mikros, small + phyllon, leaf) a leaf whose trace is not marked with a gap in the stem's vascular system; microphylls are thought to represent epidermal outgrowths

Micropyle

(Gr. mikros, small + pyle, orifice, gate) a pore leading from the outer surface of the ovule between the edges of the two integuments down to the surface of the nucellus

Microsporocyte

(Gr. mikros, small + spora, seed + L. cyta, vessel) a diploid cell in which meiosis will occur, resulting in four microspores; synonymous with microspore mother cell

Microspore

(Gr. mikros, small + spore) a spore that, in vascular plants, gives rise to a male gametophyte

Microtubule

(Gr. mikros, small + tubule, dim. of tube) a tubule 25 nm in diameter and of indefinite length, occurring in the cytoplasm of many types of cells; major components of the spindle during cell division

Mitosis (plural, mitoses)

(Gr. mitos, a thread) nuclear division, involving appearance of chromosomes, their longitudinal duplication, and equal distribution of newly formed parts to daughter nuclei

Spongy parenchyma

cells making up the spongy mesophyll

Free energy

the internal thermodynamic potential of a portion of matter; change in free energy during a chemical reaction determines the direction of the reaction

Climax community

the last stage of a natural succession; a community capable of maintaining itself as long as the climate does not change

Reradiation

the loss of long-wave radiation back to space

Test cross

the mating between a recessive homozygote and the corresponding dominant to determine whether the latter is homozygous or heterozygous

Permanent wilting percentage

the maximum amount of water (expressed as percentage of the dry weight of the soil) that a soil can hold that is unavailable to a plant

Osmotic potential

the maximum theoretical suction that can be developed in a solution as a result of osmosis when the solution is placed in an osmometer surrounded by pure water; it is a measure of the concentration of the solute(s)

Plantae

the monophyletic kingdom of life that includes all green plants and some algae

Fungi

the monophyletic kingdom that contains all true fungi

Epidermal cells

the most abundant cell type in the epidermis; typically lack chloroplasts

Base pair

the nitrogen bases that pair in the DNA molecule, adenine with thymine and guanine with cytosine

Density

the number of individuals per unit area; for example, 200 red oak trees per hectare; sometimes a term used to describe the degree of canopy closure, as "canopy density of 35%" would mean that the plant canopy covers 35% of the ground area

Species richness

the number of species present in an area, rare species being counted as equal to common species

Dimorphism

the occurrence of two growth forms at different stages in the life of an organism; an example is the occurrence of yeast and mycelial forms in some fungi

Endomembrane system

the organelles in a cell that exchange patches of membranes, including the nuclear envelope, endoplasmic reticulum, and Golgi apparatus

Parent material

the original rock or depositional matter from which the soil of a region has been formed

Exodermis

the outer layer of the cortex in certain roots; sometimes has Casparian strips

Selection pressure

the overall effect of environmental factors in determining the direction of natural selection

Pith

the parenchymatous tissue occupying the central portion of a stem

Primary phloem

the part of the phloem differentiated from the procambium during organ elongation

Primary xylem

the part of the xylem differentiated from the procambium during organ elongation

Food chain

the path along which caloric energy is transferred within a community (from producers to consumers to decomposers)

Life cycle

the pattern of transfer of genetic information in a species from parent to offspring, or from generation to generation

Primary structure

the peptide bonds holding the amino acids of a protein together; the sequence of amino acids in a protein

Genetic code

the relationship between codons (sequences of three bases) in DNA or messenger RNA and the amino acids they specify in a protein

Cell cycle

the repeating sequence of events involved in the reproduction of a eukaryotic cell, including G1, S (DNA synthesis), G2, and M (mitosis and cytokinesis) phases

Sclerieds

cells typically with thick secondary cell walls and irregular shapes, one of two categories of cell types making up sclerenchyma tissue

Extreme halophiles

certain Archaea capable of living in hypersaline habitats

Transformation

change in the genotype of bacteria by the direct uptake, incorporation, and expression of extracellular DNA

Aseptate

characteristic of a hypha that is not divided into cell-like compartments by regularly spaced cross walls

Leaf scar

characteristic scar on a stem axis made after leaf abscission

Attributes

characteristics that have to do with community architecture, species richness, the spatial patterns in which individuals are arranged, the efficiency with which they trap sunlight and cycle energy or nutrients through the community, and the stability of the associated species in the face of environmental stress or change

Nucleotides

components of nucleic acid: nucleoside (nitrogen base + sugar) + phosphoric acid

Nucleosides

components of nucleic acids consisting of a nitrogen base and a sugar; in DNA, the sugar is deoxyribose, and in RNA, ribose; adenine, guanine, and cytosine occur in both DNA and RNA, thymine occurs in DNA, and uracil occurs in RNA

Photosystems I and II

components of the noncyclic electron transport system of the light reactions of photosynthesis

Codominance

concerning alleles of a gene, sharing in influence; the trait produced by two codominant alleles is intermediate between (or different from) that produced by either alone; also incomplete dominance

Heterophylly

condition where a plant has leaves of more than one shape

Microgametophyte

consists of a layer of cells inside the spore wall forming an antheridium, and a mass of sperm cells in the center

Dermal tissue system

consists of the outer tissues of the plant body, epidermis (a primary tissue) and the periderm (a secondary tissue); functions to protect the plant body from drying, pathogens, and insects

Coevolution

coordinated evolution of two or more species, driven by interactions that cause changes in each species to favor changes in the other species

Nonequilibrium paradigm

currently, a widely accepted view of natural vegetation, which holds that natural disturbances are so common that the landscape is largely composed of stands of successional vegetation, and one consequence is that the landscape is rich in species

Natural selection

differential reproductive success of varied genetically determined phenotypes in a population, resulting from interactions with the environment; see also directional, diversifying, and stabilizing selection

Shoot apical meristem (SAM)

dividing cells responsible for differentiation of all primary meristems and primary tissues of the shoot

Secondary meristem

dividing cells responsible for lateral growth of stems and roots of vascular plants; there are two types: vascular cambium and cork cambium

Lateral root primordium

early stage of lateral root

Palisade parenchyma

elongated photosynthetic cells, containing many chloroplasts, found just beneath the upper epidermis of leaves; also called palisade mesophyll

Eyespot

enables the organism to orient itself toward the light

Kinetic energy

energy associated with moving objects; the energy of a body associated with its motion

Potential energy

energy associated with position; concerning a chemical reaction, includes the energy of a set of reactants associated with the position of their constituent atoms and the shape of their bonding orbitals

Microcapillary space

exceedingly small spaces, such as those found between microfibrils of cellulose

Elaiosomes

food bodies on certain plants; eaten by insects, especially ants

Capillary forces

forces that pull water into the narrow space between hydrophilic surfaces; includes adhesive force beween water and the surfaces and cohesive force between water molecules

Axile

form of placentation where the ovules are attached along the central axis of the ovary

Primary thickening meristem

found in the shoot tip of monocots; generates growth in length and width

Sapwood

functional xylem at the periphery of secondary stems; contrast to Heartwood

Imperfect fungi

fungi reproducing only by asexual means

Tracheary element

general term for the conducting elements in xylem, a vessel member or tracheid

Indeterminate

generally, having no defined limits; in plant development, a morphogenetic process that produces new organs or sections of an organ while preserving a meristem in which new cells are formed to continue the process indefinitely

Translation

generally, rendering from one language into another; specifically, the use of a sequence of RNA bases to specify a sequence of amino acids in the process of protein synthesis

Species epithet

the second word in a binomial species name, which distinguishes the named species from other species in the same genus

Axial system

the secondary vascular cells oriented parallel to the long axis of a stem or root

Fiddlehead

the shape of young fern leaves (fronds) as they push up through the soil: tightly coiled like the head of a violin

Matrix

the solution of enzymes in the central chamber of a mitochondrion

Light harvesting complexes

groups of chlorophyllcontaining proteins in thylakoid membranes that absorb light and transfer the energy to photoreaction centers P680 or P700

Nonpolar

having a uniform distribution of electric charge

Heterokaryotic

having nuclei of more than one genotype in uncontrolled proportions within a single living body

Deoxyribonucleic acid (DNA)

hereditary material; long, double-stranded polymer of nucleotides A, T, G, and C

Wood Age

the span of history during which wood was the, or one of the, principal materials for houses, fuel, and vehicles; considered by some to include the Stone Age, Bronze Age, Iron Age, Industrial Age, Nuclear Age, and up to the present

Parsimony (Principle of)

in cladistics, the postulate that the cladogram requiring the fewest evolutionary steps is most likely to be correct; that cladogram is said to be the most parsimonious

Ingroup

in cladistics, the set of taxa that is the target of study

Speciation

the splitting of one species into two species

Hybridization

in evolution, the formation of progeny by a mating between organisms of different species

Character

in genetics and cladistics, a distinctive trait or aspect of the phenotype, controlled by one or more genes; it may be a detail of body form, either physical or chemical, or the organism's function or behavior

Locus

in genetics, a site on a chromosome identified by recombinational analysis; the position of a gene

Wild type

in genetics, the gene normally occurring in the wild population, usually dominant

Recessive

in heredity, referring to an allele that, when present in a hybrid with a contrasting allele, is not expressed in the phenotype

Cap

in mushrooms, the umbrella-like portion in which meiospores are made

Determined

in plant development, a tissue having a limited number of developmental possibilities

Variety

in taxonomy, a subgroup within a species; also called a cultivar (in cultivated plants), pathovar (in pathogenic organisms), or a race (in animals)

Double fertilization

in the embryo sac, the fusion of the egg and sperm and the simultaneous fusion of the second male gamete with polar nuclei

Domain

in the taxonomic hierarchy, a group that contains one or more kingdoms

Form

in the taxonomic hierarchy, a subgroup within a species, equivalent to race or variety

Annual ring

in wood, a layer of growth formed during one year and consisting of springwood and summerwood

Zygosporangium

in zygomycete fungi, a sporangium in which a zygospore is made by fusing two unicellular gametangia

Germ sporangium

in zygomycete fungi, the sporangium produced a hypha that grows directly from the germinating zygospore

Freshwater wetlands

include riparian vegetation along the banks of rivers, lakes, springs, and sinks

Woody perennial

include subshrubs, shrubs, vines, and trees

Central cell

large cell making up the central portion of the embryo sac

LAI

leaf area index; a ratio that summarizes the surface area of all leaves that shade a given area of ground, a dimensionless number usually between 1 and 11

Lipid body

lipid storage organelle found in seeds

Spongy mesophyll

loosely organized photosynthetic cells of a leaf

Synapsis

the stage of meiosis when homologous chromosomes pair up on the spindle apparatus

Pollination

the transfer of pollen from a stamen or staminate cone to a stigma or ovulate cone

Cross-pollination

the transfer of pollen from a stamen to the stigma of a flower on another plant, except in clones

Active transport

the transport of a substance across a cellular membrane by a mechanism that expends cellular energy to control the net direction of transport.

Polar nuclei

the two nuclei of the central cell in the embryo sac of flowering plants

Leaf trace

the vascular bundle extending from the stem to the base of a leaf

Analogous traits

traits that have a similar form, function, or both, but were not evolved from the same ancestral trait; contrast with homologous traits

Self-pollination

transfer of pollen from the stamens to the stigma of either the same flower or flowers on the same plant

Open dichotomous venation

veins in leaves that repeatedly branch into unequal portions

Netted venation

veins of leaf blade visible to the unaided eye, branching frequently and joining again, forming a network

Sieve plate

wall area in a sieve-tube member containing a region of pores through which pass strands connecting sieve-tube protoplasts

Secondary wall

wall material deposited on the primary wall in some cells after elongation has ceased

Unavailable water

water held by the soil so strongly that root hairs cannot readily absorb it

Polygenes

many genes influencing the development of a single trait; results in continuous variability; compare Allele

Grade of evolution

members of a clade that are far more successful than the rest because of special traits they share

Residual meristem

meristematic region near the shoot tip that remains after differentiation of the pith and cortex

Primary meristems

meristems of the shoot or root tip giving rise to the primary tissues—protoderm, ground meristem, and procambium

Microsporidia

microscopic unicellular eukaryotic parasites of humans and other animals, characterized by lack of mitochondria and by entering host cells through an everted membranous tube

Alfisol

modified podzol soil, typical of the northern part of the deciduous forest

Haustorial root

modified root of certain parasitic plants, such as dodder, that penetrates into the host plant

Cyclic electron transport

movement of electrons in thylakoid membranes through a closed pathway that does not result in net oxidation or reduction of any intermediate; the movement is stimulated by light and generates a chemiosmotic gradient that provides energy for the synthesis of ATP

Endosperm mother cell

one of the seven cells of the mature embryo sac, containing the two polar nuclei and, after reception of a sperm cell, giving rise to the primary endosperm cell from which the endosperm develops

Generative cell

one of the two cells making a pollen grain; will divide to form two sperm cells

G1

period of cell cycle preceding DNA synthesis

G2

period of cell cycle preceding mitosis

P680 and P700

photoreaction centers of photosystem I (700) and photosystem II (680) in thylakoid membranes of chloroplasts

Phycobiliproteins

pigments found in the red algae and cyanobacteria, similar to bile pigments and always associated with proteins

Simple pistil

pistil that consists of only one carpel

Simple pit

pit in a secondary cell wall not surrounded by an overarching border; contrast to bordered pit

Helophyte

plant species that are able to grow in saturated soil such as marshes and bogs

Short-day plants

plants that are induced to flower only when the length of the day decreases to less than a certain value

Long-day plants

plants that are induced to flower only when the length of the day exceeds a certain value

Sieve-tube members

portion of a sieve tube composed of a single protoplast and separated from other sieve-tube members by sieve plates

Shoot tip

portion of the shoot containing apical and primary meristems and early stages of differentiation

Dicotyledonous

possessing two cotyledons

Root pressure

pressure developed in the root as the result of osmosis and inducing guttation

Residual procambium

procambial cells that did not develop into primary xylem or primary phloem located between the arcs of xylem and phloem

Genetic drift

random changes in the ratio of alleles that occur in small populations as a result of chance events

Transduction

recombination that occurs when a virus transfers host DNA from one host organism to another

NADH

reduced NAD

NADPH

reduced NADP

Inorganic

referring in chemistry to compounds that do not contain carbon

Organic

referring in chemistry to the carbon compounds, many of which have been in some manner associated with living organisms

Ovulate

referring to a cone, scale, or other structure bearing ovules

Differentially permeable

referring to a membrane through which different substances diffuse at different rates; some substances may be unable to diffuse through such a membrane

Whorled

referring to bud or leaf arrangement in which there are three or more buds or three or more leaves at a node

Opposite

referring to bud or leaf arrangement in which there are two buds or two leaves at a node

Alternate

referring to bud or leaf arrangement in which there is one bud or one leaf at a node

Soil texture

refers to the amounts of sand, silt, and clay in a soil, as sandy loam, loam, or clay texture

Root apical meristem (RAM)

region of cells located at the root tip; derives the cells and tissues of the root

Progymnosperms

represent an intermediate form, or "missing link," revealing the transition from a spore-releasing vascular plant to a seed plant

Sexual reproduction

reproduction that requires meiosis and fertilization for a complete life cycle

Crustose

said of a lichen that grows firmly attached to the substrate along its entire lower surface

Bundle scar

scar left where conducting strands passing out of the stem into the leaf stalk were broken off when the leaf fell

Ulvophyceae

sea lettuces, typically small, green seaweeds composed of thalli growing attached to a substrate in shallow water

F2

second filial generation, obtained by crossing two members of the F1, or by self-pollinating the F1

Springwood

secondary xylem (wood) that forms early in the growing season; earlywood

Summerwood

secondary xylem (wood) that forms late in the growing season; latewood

Latewood

secondary xylem that forms in wood late in the growing season; summerwood

ATP

see Adenosine triphosphate

Archaebacteria

see Archaea

Species name

see Binomial

Grain

see Caryopsis

Incomplete dominance

see Codominance

Blue-green algae

see Cyanobacteria

DNA

see Deoxyribonucleic acid

Dikaryon

see Dikaryotic mycelium

ER

see Endoplasmic reticulum

IAA

see Indoleacetic acid

Pod

see Legume

Pollen mother cell

see Microsporocyte

Deuteromycete

see Mitosporic fungus

Root nodule

see Nodule

Division

see Phylum

Whisk ferns

see Psilophytes

RNA

see Ribonucleic acid

Carboxylase/oxygenase (rubisco)

see Ribulose bisphosphate carboxylase

Ribulose bisphosphate

see Ribulose bisphosphate carboxylase

Bracket fungus

see Shelf fungus

Citric acid cycle

see Tricarboxylic acid cycle

Tepals

sepals and petals that are indistinguishable

Leaflet

separate part of the blade of a compound leaf

Spine

sharp pointed structure, a modified leaf

Thorn

sharply pointed woody structure; a modified branch

Bundle sheath

sheath of parenchyma or sclerenchyma cells that surround the vascular bundles of leaves, sometimes called border parenchyma

Guard cells

specialized epidermal cells found on young stems and leaves; between each pair of guard cells is a small pore through which gases enter or leave; a pair of guard cells in addition to the pore constitute a stoma

Casparian strip

suberized strip that impregnates the radial and transverse wall of endodermal cells

Ectotrophic mycorrhizae

symbiotic relationship between roots and fungi

Noncyclic photophosphorylation

synthesis of ATP through noncyclic electron transport

Cyclic photophosphorylation

synthesis of ATP through the cyclic electron transport

Ray system

system of cells in secondary tissues that are oriented perpendicular to the long axis of the stem, formed from ray initials of the vascular cambium

Ecotone

where two or more communities and environments grade into each other

Recessive character

that member of a pair of Mendelian characters that, when both members of the pair are present, is subordinated or suppressed by the other, dominant character

Primary endosperm nucleus

the 3n product of the fertilization of one sperm nucleus with the two polar nuclei; the endosperm develops from this

C3 cycle

the Calvin Benson cycle of photosynthesis, in which the first products after CO2 fixation are three-carbon molecules

Coal Age

the Carboniferous period, beginning 345 million years ago and ending 280 million years ago

C4 cycle

the Hatch-Slack cycle of photosynthesis, in which the first products after CO2 fixation are four-carbon molecules

Cytoskeleton

the framework of protein filaments, including microfilaments, microtubules, and intermediate filaments, in the cytoplasm

Conk

the fruiting body of a bracket fungus

Linkage

the grouping of genes on the same chromosome

Activation energy

the increase in potential energy of a complex of two or more molecules required for a chemical reaction

Convergent evolution

the independent evolution of similar traits by two taxa that were originally quite different, resulting from exposure to similar selection pressures

Herbivory

the ingestion of plants by animals

Feedback inhibition

the inhibition of an enzyme by its product or the product of the metabolic pathway of which it is a part

Apical dominance

the inhibition of lateral buds or meristems by the apical meristem

Hardy-Weinberg equilibrium

within a population, constancy of the ratio of alternative alleles for a particular gene from one generation to the next

Heartwood

wood in the center of old secondary stems that is plugged with resins and tyloses and is not active

Earlywood

wood that forms from vascular cambium early in the growing season; synonym for springwood

Diffuse porous

wood with an equal and random distribution of large xylem vessel members throughout the growth season

Ring porous wood

wood with large xylem vessel members mostly in early wood; compare with Diffuse porous wood

Fiber-tracheid

xylem elements found in pine that are structurally intermediate between tracheids and fibers

Electron microscope

a microscope that uses a beam of electrons rather than light to produce a magnified image

Pit

a minute, thin area of a secondary cell wall

Bud scale

a modified protective leaf of a bud

Glycolipid

a molecule consisting of a combination of one or more sugars with a hydrocarbon

Hydrocarbon compound

a molecule formed from hydrogen and carbon

Recombinant DNA

a molecule of DNA formed by the joining of segments from different sources

Urediniomycetes

a monophyletic class of basidiomycete fungi that lack basidiomata and cause rust diseases in plants

Ustilagomycetes

a monophyletic class of basidiomycete fungi that lack basidiomata and often cause smut diseases in plants

Hymenomycetes

a monophyletic class of basidiomycete fungi, characterized by dolipore septa and complex basidiomata

Glomeromycota

a monophyletic phylum in kingdom Fungi, noted for members engaging in arbuscular endomycorrhizae

Subalpine zone

a montane zone in which the tree growth form becomes diminished and scattered; a transition between montane forest and alpine tundra

Indoleacetic acid

a naturally occurring growth regulator, an auxin

Ribonucleic acid (RNA)

a nucleic acid containing the sugar ribose, phosphorus, and the bases adenine, guanine, cytosine, and uracil; present in all cells and concerned with protein synthesis in the cell

Thymidine

a nucleoside incorporated in DNA, but not in RNA

Arbuscule

a nutrient-transferring mycelial structure made by a glomeromycete fungus in endomycorrhizal association with a host plant; consisting of highly branched hyphae, it forms in the space enclosed by the walls of a single host plant cell

Peptidoglycan

a particular macromolecule that makes up the walls of Bacteria, including cyanobacteria

Progressive succession

a pathway of succession that results in higher species richness, greater biomass, higher physiognomic complexity, more continuous plant cover, and a microenvironment that is more buffered from the macroenvironment

Retrogressive succession

a pathway of succession that results in lower species richness, less biomass, lower physiognomic complexity, less plant cover, and a microenvironment less buffered from the macroenvironment

Template

a pattern or guide used in manufacturing; a sequence of DNA bases used to specify the sequence of synthesis of a complementary strand of DNA or RNA

Herbaceous perennial

a perennial plant without any wooden parts; an herbaceous plant capable of dying aboveground every year, but remaining alive belowground, and thus being able to vegetatively recover every year; lifespans are one to several decades

Consensus tree

a phylogenetic tree that has all the features shared by the equally parsimonious cladograms in a study, while leaving conflicts unresolved; also called a consensus cladogram

Accessory pigment

a pigment that absorbs light energy and transfers energy to chlorophyll a

Bordered pit

a pit in a tracheid, vessel member, or sometimes a fiber having a distinct rim of the cell wall overarching the pit membrane

Powdery mildew

a plant disease caused by certain parasitic ascomycete fungi, characterized by a dusty white layer of conidia on infected leaves

Rust disease

a plant disease caused by urediniomycete fungi (phylum Basidiomycota), named for the rust-colored mitospores that often form on infected leaves and stems

Smut disease

a plant disease caused by ustilagomycete fungi (phylum Basidiomycota), named for greasy black masses of fungal mitospores that form on the host plant

Abscisic acid

a plant hormone variously inducing abscission, dormancy, stomatal closure, growth inhibition, and other responses in plants

Drought-deciduous

a plant that loses its leaves during dry periods (as opposed to winter-deciduous)

Carrageenan

a polysaccharide found in the walls of red algae that reacts with milk proteins to make a stable, creamy, thick solution or gel

Functional group

a portion of a biochemical molecule that participates in a chemical reaction; sulfhydryl (-SH) and amino (-NH2) groups in proteins are functional groups

Cell wall

a protective meshwork of molecules enclosing an Archaeal, Bacterial, fungal, protist, or plant cell; usually secreted by the cell

Ion pump

a protein in a cellular membrane that catalyzes the transport of an ion from one side of the membrane to the other; pump implies that the transport is active, requiring the expenditure of metabolic energy and potentially occurring from a smaller concentration of the ion to a greater concentration

Guanine

a purine base found in DNA and RNA

Adenine

a purine base present in nucleic acids and nucleotides

Cytosine

a pyrimidine base found in DNA and RNA

Uracil

a pyrimidine found in RNA but not in DNA

Thymine

a pyrimidine occurring in DNA, but not in RNA; 3H-thymidine is radioactive thymidine used to indicate and locate DNA synthesis

Photon

a quantum of light; the energy of a photon is proportional to its frequency; E = hv, where E is energy; h, Planck's constant, 6.62 x 10-27 erg-second; and v is the frequency

Plastoquinone

a quinone, one of a group of compounds involved in the transport of electrons during photosynthesis in chloroplasts

Photophosphorylation

a reaction in which light energy is converted into chemical energy in the form of ATP produced from ADP and inorganic phosphate

Phosphorylation

a reaction in which phosphate is added to a compound, for example, the formation of ATP from ADP and inorganic phosphate; many enzymes are stimulated (or inhibited) by the addition of phosphate

Hypersensitivity response

a reaction of plant cells to the presence of pathogenic agents, involving a loss of ions, the synthesis of reactive oxygen species (superoxide, hydrogen peroxide), and eventual death

Active site

a region of an enzyme whose shape permits the binding of substrates and where catalytic activity takes place

Phytochrome

a reversible pigment system of protein naturally found in the cytoplasm of green plants; it is associated with the absorption of light that affects growth, development, and differentiation of a plant, independent of photosynthesis, for example, in the photoperiodic response

Bud scar

a scar left on a twig when the bud or bud scales fall away

Form genus

a scientific name given to an organism from the fossil record, when only a portion of the entire plant has been recovered and is known

Dolipore septum

a septum in which the wall around the septal pore is thickened (the dolipore) and parenthesomes occur on both sides of the septum; found only in dikaryotic mycelia of hymenomycete fungi

Base sequence

a sequence of nucleotide bases in DNA or RNA potentially containing information used to direct the synthesis of a protein

Codon

a sequence of three bases (nucleotides) along the RNA molecule that code for a single amino acid

Sieve tube

a series of sieve-tube members forming a long, cellular tube specialized for the conduction of food materials; found in flowering plants

Hierarchy

a set of categories that has nested levels, such as the Linnaean system of taxonomy

Metabolic pathway

a set of compounds related by enzymatically catalyzed chemical reactions, such that the first compound is transformed into the second, the second into the third, and so on

Subshrub

a shrub that is shorter than 30 cm in height, and which is woody only at the base of its stems; the life span of subshrubs is shorter than that of shrubs, only one to several decades

Berry

a simple fleshy fruit, the ovary wall fleshy and including one or more carpels and seeds

Tap root system

a single primary root with lateral branches

Horsetails

a small group of 25 species within a single genus, Equisetum, which have stems that are hardened by ridges and an epidermis containing silica; branching occurs in whorls, and leaves are reduced; classified in this text among the monilophyte lineage with whisk ferns, ophioglossalean ferns, marattialean ferns, and true ferns

Gnetophytes

a small group of seed plants with life cycles having some traits of gymnosperms and some of angiosperms; once thought to be ancestral to flowering plants, they are now considered to be a sister group to angiosperms and gymnosperms

Basal angiosperms

a small group of species (<200) thought to be ancestral to all other monocots and dicots; includes water lilies, star anise, and Amborella

Pheromone

a small molecule that functions as a chemical signal between organisms, being released by one organism and received by others, where it causes changes in behavior, physiology, or development

Isidium (plural, isidia)

a small outgrowth of a lichen that accomplishes asexual reproduction by pinching off to form a new lichen

Orbital

a solution of the Schrodinger wave equation describing a possible mode of motion of a single electron in an atom or molecule

Micropylar chamber

a space interior to the micropyle of an ovule, across which pollen grains can be carried to the female gametophyte by a drying pollination drop

Organelle

a specialized region within a cell, such as the mitochondrion or dictyosome

Indicator species

a species that has a narrow range of tolerance for one or more environmental factors so that, from its occurrence at a site, one can predict these factors at that site (for example, nutrient availability or summer temperatures)

Dikaryotic stage

a stage in the sexual life cycle of a dikaryomycete fungus, consisting of a dikaryotic mycelium

Archegoniophore

a stalked structure on which female gametangia are produced, as with the liverwort Marchantia

Antheridiophore

a stalked structure on which male gametangia are produced, as with the liverwort Marchantia

Runner

a stem that grows horizontally along the ground surface

Stomatal apparatus

a stoma plus the surrounding subsidiary cells

Vascular bundle

a strand of tissue containing primary xylem and primary phloem (and procambium, if present) and frequently enclosed by a bundle sheath of parenchyma or fibers

Cell plate

a structure that forms at the equatorial plane of the cell at right angles to the spindle fibers during cytokinesis; the precursor of the middle lamella

Meiosporangium

a structure within which one or more diploid cells undergo meiosis, producing meiospores, each of which can germinate and produce a plant that represents the male gametophyte generation

Hydrogen acceptor

a substance capable of accepting hydrogen atoms or electrons in the oxidation-reduction reactions of metabolism

Lipopolysaccharide

a substance containing lipid and a carbohydrate polymer; —layer, the outer membrane of a gram-negative bacterium

Adenosine triphosphate (ATP)

a substance formed in metabolism from ADP and inorganic phosphate; the most prominent and universal molecule that acts as a carrier of energy in metabolism

Base

a substance that can accept a proton (H+); also, the purine and pyrimidine groups in nucleic acids and nucleotides are collectively called bases

Coenzyme

a substance, usually nonprotein and of low molecular weight, necessary for the action of some enzymes

Neritic zone

a subtidal but relatively shallow offshore zone, often dominated by large kelps

Primary succession

a successional path that begins on recently exposed land that has never before supported vegetation; hence, it has no soil profile or buried plant propagules

Secondary succession

a successional pathway that begins with bare land that was once-vegetated and ends with vegetation that had occupied the land before some catastrophic disturbance, such as flood, overgrazing, clearcutting, fire, or conversion to agriculture

Parasitism

a symbiotic relationship in which one organism (the parasite) benefits, whereas the other (the host) is harmed

Flowering plants

a synonym for angiosperms; plants that produce seeds inside an enlarged ovary, which at maturity is called a fruit

Ice Age

a synonym for the Pleistocene epoch, generally defined as the period between 2 million and 10,000 years ago; during the Pleistocene epoch, there were at least five glacial advances, separated by interglacial warm periods

Tricarboxylic acid cycle

a system of reactions that contributes to the catabolic breakdown of foods in respiration and that provides building materials for a number of anabolic pathways; also called the Krebs cycle and the citric acid cycle

Character matrix

a table that compares states of shared characters in selected taxa

Scanning electron microscopy

a technique by which the surface of a subject is visualized at high resolution by bombarding it with a tighly focused beam of electrons, measuring the rate at which electrons are scattered into a collector as a function of the position of the beam, and displaying the result on a television screen by coordinating the scanning of the electron beam hitting the sample with the electron beam in the television tube

Confocal microscopy

a technique in which the illumination and objective lens of a microscope are focused on only one point of a sample on a microscope stage at a time, eliminating light scattering and increasing resolution and contrast

Transmission electron microscopy

a technique of visualizing an object at high resolution by focusing a beam of electrons through the object onto a fluorescent screen or photographic film

Mediterranean climate

a temperate-zone climate type featuring dry, hot summers and cool, wet winters; frosts are uncommon and annual precipitation is 25 to 75 cm; found in five parts of the world: Australia, South Africa, Chile, California, and around the Mediterranean Sea

Polar

a term applied to molecules having a nonuniform distribution of electrons and thus negatively and positively charged regions

Mating test

a test to determine whether organisms of two populations will spontaneously interbreed and produce fertile offspring when brought together under natural conditions; the basis for defining biological species

Hydrogen bond

a weak bond in which a hydrogen atom interposes between and holds together two strongly electronegative atoms (for example, oxygen, nitrogen)

Character states

alternative forms that a given character may take

Methanogen

an Archaeal organism that derives energy by catalyzing the reduction of carbon and oxidation of H2, forming methane and water

Nucleic acid

an acid found in all nuclei, first isolated as part of a protein complex in 1871 and separated from the protein moiety in 1889; all known nucleic acids fall into two classes: DNA and RNA; they differ from each other in the sugar, in one of the nitrogen bases, in many physical properties, and in function

Montane

an adjective, meaning in or of the mountains; montane vegetation grows at significant elevations within mountain chains

Preprophase band

an aggregation of microtubules, occurring in the G2 phase of a plant cell cycle, which marks the plane of cell division after the next mitosis

Lithotroph

an alternate name for chemoautotroph that derives energy from the oxidation of inorganic compounds

Holdfast

an anchoring organ in certain seaweeds; not a true root because it lacks vascular tissue; furthermore, most absorption occurs elsewhere on the thallus

Hardwood

an angiosperm tree; having wood that is dense and more difficult to work than the wood of a conifer

Penicillin

an antibiotic derived from the mold Penicillium

Zygomycota

an artificial (nonmonophyletic) phylum in kingdom Fungi, characterized by formation of zygospores, aseptate hyphae, mitosporangia, and lack of swimming cells

Chytridiomycota

an artificial (nonmonophyletic) phylum in kingdom Fungi, containing all true fungi that have swimming reproductive cells

Egg apparatus

an egg cell and two synergid cells in the embryo sac

Rootstock

an elongated, underground, horizontal stem

Mitosporangium

an enclosure in which mitospores are made

Biological clock

an endogenous timing mechanism inferred to exist in cells to explain various cyclical behaviors

Selective agent

an environmental factor that causes natural selection

Restriction enzyme

an enzyme that hydrolyzes DNA at a particular base sequence (specific to the type of enzyme); also called restriction endonuclease

ATP synthetase

an enzyme that produces ATP from ADP and phosphate, using as an energy source the flow of protons across a membrane in response to a concentration gradient or electrical potential difference

Type specimen

an example organism that is placed on file when its species is first formally named

Seedling hypothesis

an explanation, first offered by William Bond, for the dominance of angiosperms over gymnosperms; angiosperm seedlings typically are fast growing, contain more efficient tissues for conducting water and nutrients, and build relatively flimsy tissue that requires a low caloric investment

Primary consumer

an herbivorous organism, gaining nutrition from plants (producers)

Stomatal crypt

an indentation on the surface of a leaf into which stomata open; regulates transpiration by providing a relatively stable boundary layer of air outside the stomata

Head

an inflorescence; typical of the composite family, in which flowers are grouped closely on a receptacle

True fungi

an informal term for organisms that belong to kingdom Fungi

Microfilament

an intracellular organelle; threadlike, formed of actin subunits, and often participating in the movement of other organelles around the cell

Scientific method

an iterative process of stating, testing, and refining hypotheses that best explain natural phenomena

Vallecular canal

an open canal in the cortex of horsetail stems, arranged with others in a circle, alternating with vascular bundles; the function may be to transport air to belowground rhizomes and roots

Carinal canal

an open canal, devoid of cells, which may function to transport air down through the cortex to underground rhizomes and roots; characteristic of horsetail stems

Alismatales

an order of plants that is a basal clade or group to the rest of the monocots; includes a variety of aroids and aquatic plants

Peroxysome

an organelle of the microbody class that contains enzymes capable of making and destroying hydrogen peroxide, including glycolic oxidase and catalase

Pyrimidine

an organic base having a single-ring structural formula

Halophile

an organism adapted to living in a high-salt environment; a group of Archaea are halophiles

Obligate anaerobe

an organism obliged to live in the absence of oxygen

Obligate parasite

an organism obliged to live strictly as a parasite

Obligate saprophyte

an organism obliged to live strictly as a saprophyte

Chemoheterotroph

an organism that obtains both energy and carbon from organic sources

Chemoautotroph

an organism that oxidizes reduced inorganic compounds such as H2S to obtain energy and that uses CO2 as a carbon source

Seedless vascular plant

an organism with an embryo life cycle phase and with xylem and phloem, but which reproduces with spores rather than seeds; includes the lycophytes and the monilophytes

Superior ovary

an ovary completely separate and free from the calyx

Inferior ovary

an ovary partially or completely united with the calyx

Leaf axil

angle formed by the leaf stalk and the stem

Wetland

any area that remains wetted throughout the soil profile for a sufficient length of time each year to produce anaerobic conditions in the soil; characterized by the dominance of flood-tolerant plant species

Oxidation-reduction (redox)

any chemical reaction in which electrons are transferred from one molecule to another

Boreal forest

any forest at low elevations in the boreal zone, a north-temperate belt between the arctic and temperate zones; these forests are usually dominated by conifers

Lysis

(Gr. lysis, a loosening) a process of disintegration and cell destruction

Thermoacidophiles

a group of Archaea that is adapted to live in hot, acid environments

Companion cell

cell associated with sieve-tube members

Fucoxanthin

(Gr. phykos, seaweed + xanthos, yellowish brown) a brown pigment found in brown algae

Conifer

(cone + L. ferre, to carry) a cone-bearing tree

Conidiophore

(conidia + Gr. phoros, bearing) a hypha that makes and releases conidia

Conidiospore

(conidia + spore) spore formed as described for conidia

Amoeboid

(Gr. amoibe, change) eating or moving by means of temporary cytoplasmic extensions from the cell body

Anisogamy

(Gr. an, prefix meaning not + isos, equal + gamete, spouse) the condition in which the gametes, although similar in appearance, are not identical

Anabolism

(Gr. ana, up + metabolism) the constructive phase of metabolism, in which more complex molecules are built from simpler substances

Atoms

(F. atome, from the Gr. atomos, indivisible) the smallest particles in which the elements combine either with themselves or with other elements, and thus the smallest quantity of matter known to possess the properties of a particular element; a unit of matter consisting of a dense, central nucleus, consisting of several positively charged protons and uncharged neutrons, surrounded by a number of negatively charged electrons

Ribulose bisphosphate carboxylase

(F. carbboe, carbon + Gr. oxys, acidic) the enzyme of photosynthesis that catalyzes the initial fixation of carbon, that is, the covalent attachment of carbon in CO2 to an organic molecule, ribulosebisphosphate

Ciliates

(F. cil, an eyelash) one group of motile protists in the alveolate clade; contains some organisms previously classified as protozoa, for example, Paramecium, capable of swimming by the synchronized action of many cilia

Cilia (singular, cilium)

(F. cil, an eyelash) protoplasmic hairs that, by a whiplike motion, propel certain types of unicellular organisms, gametes, and zoospores through water

Development

(F. developper, to unfold) developmental changes of a cell, tissue, or organ leading to the presence of features that equip that cell, tissue, or organ for performing specialized functions

Etiolation

(F. etioler, to blanch) a condition involving increased stem elongation, poor leaf development, and lack of chlorophyll, found in plants growing in the absence, or in a greatly reduced amount, of light

Flower

(F. fleur, L. flos, a flower) floral leaves grouped together on a stem and adapted for sexual reproduction in the angiosperms

Liana

(F. liane from lier, to bind) a plant that climbs on other plants, depending on them for mechanical support; a plant with climbing shoots

Molecule

(F. mole, mass + cule, dim.; literally, a little mass) a unit of matter, the smallest portion of an element or a compound that retains chemical identity with the substance in mass; the molecule usually consists of a union of two or more atoms; some organic molecules contain a large number of atoms

Ovule

(F. ovule, from L. ovulum, dim. of ovum, egg) a rudimentary seed containing, before fertilization, the female gametophyte, with egg cell, all being surrounded by the nucellus and one or two integuments

Oxidation

(F. oxide, oxygen + tions, suffix denoting action) to increase the positive valence or decrease the negative valence of an element or ion; loss of an electron by an atom

Parietal

(F. parietal, attached to the wall, from L. paries, wall) belonging to, connected with, or attached to the wall of a hollow organ or structure, especially of the ovary or cell

Reduction

(F. reduction, L. reductio, a bringing back) originally "bringing back" a metal from its oxide, that is, iron from iron rust or ore; any chemical reaction involving the removal of oxygen from or the addition of hydrogen or an electron to a substance; energy is required and may be stored in the process as in photosynthesis

Sucrose

(F. sucre, sugar + ose, ending designating a sugar), cane sugar (C12H22O11)

Transpiration

(F. transpirer, to perspire), the giving off of water vapor from the surface of leaves

pH

(Fr. p(ouvoir), to be able + h(ydrogene), hydrogen) a symbol for the degree of acidity (values from 0 to 7) or alkalinity (values from 7 to 14); values representing the relative concentration of the hydrogen ion in solution

Elater

(G. elater, driver) an elongated, sometimes coiled cell capable of dispersing spores from a sporangium; commonly found in liverworts

Embryophytes

(G. en, in + bryein, to swell + phyton, a plant) all members of the plant kingdom that have an embryo phase in their life cycle

Crozier

(Germanic crosse, Bishop's staff) in ascomycete fungi, a hook-shaped hypha that produces an ascus and a new crozier

Amino acid

(Gr. Ammon, from the Egyptian sun god, in N.L. used in connection with ammonium salts) an acid containing the group NH2; one of the building blocks of a protein

Taxonomy

(Gr. Taxis, arrangement + nomos, law) the science of naming, describing, and classifying forms of life

Akinete

(Gr. a, not + kinein, to move) enlarged, thickwalled, nonmotile reproductive cell produced by some cyanobacteria

Asepsis

(Gr. a, not + septos, putrid) the condition of being germ free

Asexual

(Gr. a, without + L. sexualis, sexual) any type of reproduction not involving the union of gametes or meiosis

Anaerobe

(Gr. a, without + aer, air + bios, life) an organism able to respire in the absence of free oxygen, or in greatly reduced concentrations of free oxygen

Aerobe

(Gr. aer, air + bios, life) an organism living in the presence of molecular oxygen and using it in its respiratory process

Aerenchyma

(Gr. aer, air + en, in + khein, to pour) stem or root tissue that contains irregular, large pores capable of diffusing air from aboveground organs to belowground organs

Actinomorphic

(Gr. aktis, ray + morphe, form) said of flowers of a regular or star pattern, capable of bisection in two or more planes into similar halves

Aleurone layer

(Gr. aleurone, flour) the outermost cell layer of the endosperm of wheat and other grains

Allelopathy

(Gr. allelon, mutually + pathos, suffering) synonym for amensalism; also, the special case of amensalism among plants

Allele

(Gr. allelon, of one another, mutually, each other) variant form of a gene

Antibiotic

(Gr. anti, against or opposite + biotikos, pertaining to life) a natural organic substance that retards or prevents the growth of organisms; generally used to designate substances formed by microorganisms that prevent growth of other microorganisms

Antipodal

(Gr. anti, opposite + pous, foot) cells or nuclei at the end of the embryo sac opposite that of the egg apparatus

Apogamy

(Gr. apo, away from + gamete) the process in which haploid gametophytes produce haploid sporophytes without the fusion of gametes

Apomixis

(Gr. apo, away from + mixis, a mingling) the production of offspring in the usual sexual structures without the mingling and segregation of chromosomes

Apoplast

(Gr. apo, away from + plastides, formed) the region of a plant tissue between the cells, outside of the plasma membrane of the cells that form it; contrast to Symplast

Apospory

(Gr. apo, away from + spore) the process in which diploid sporophytes produce diploid gametophytes without the occurrence of meiosis

Apothecium

(Gr. apotheke, a storehouse) a cup- or saucershaped open ascoma

Archaea

(Gr. arckhaios, ancient) a domain of prokaryotic organisms, including methane-producing, halophilic, and hot acid-dwelling forms

Ascocarp

(Gr. askos, a bag + karpos, fruit) a fruiting body of the Ascomycetes, generally either an open cup, a vessel, or closed sphere lined with special cells called asci; see Ascus

Ascomycota

(Gr. askos, a bag + mykes, fungus) a monophyletic phylum in kingdom Fungi, consisting of fungi that produce sexual spores in asci; mycelial members have septate hyphae, a dikaryotic stage in the sexual life cycle, and spread primarily by releasing conidia (mitospores)

Ascospore

(Gr. askos, a bag + spore) meiospore produced within an ascus by ascomycete fungi

Ascus (plural, asci)

(Gr. askos, a bag) a saclike cell in which ascomycete fungi produce meiospores

Autoradiograph

(Gr. auto, self + L. radioIns, a ray + Gr. graphe, a painting) a photographic print made by a radioactive substance acting on a sensitive photographic film

Autoecious

(Gr. auto, self + oikia, dwelling) having a complete life cycle on the same host

Autotrophic

(Gr. auto, self + trophein, to nourish with food) pertaining to an organism that is able to manufacture its own food

Auxin

(Gr. auxein, to increase) a plant hormone regulating cell elongation and various other aspects of development

Axil

(Gr. axilla, armpit) the upper angle between a petiole of a leaf and the stem from which it grows

Bacteria

(Gr. bakterion, a stick) a domain of prokaryotic organisms; also, common name for prokaryotes

Biotic

(Gr. biokitos, relating to life) referring to living components of the environment that affect plant life, for example, insect pollination

Biogeography

(Gr. bios, life + ge, Earth + graphein, to write) the study of the geographic distribution of organisms and the reasons for the limits to their distribution, often including distributions over geologic time and with a focus on taxonomically related organisms (families, genera); see Plant geography

Biology

(Gr. bios, life + logos, word, speech, discourse) the science that deals with living things

Biosystematics

(Gr. bios, life + synistanai, to place together) a field of taxonomy that emphasizes breeding behavior and chromosome characteristics

Bloom

(Gr. blume, flower; also IndoEuropean bhlo, to spring up) an increase in phytoplankton density sufficient to color bodies of freshwater

Botany

(Gr. botane, plant, herb) the study of plant and plantlike organisms; synonym, plant biology

Bryophytes

(Gr. bruon, moss) a group of small, mainly terrestrial plants that have an embryo life cycle phase but lack vascular tissue; contains mosses, liverworts, and hornworts

Chalaza

(Gr. chalaza, small tubercle) the region on a seed at the upper end of the raphe where the funiculus spreads out and unites with the base of the ovule

Chiasma

(Gr. chiasma, two lines placed crosswise) the microscopically visible cross formed between two chromatids of homologous chromosomes during prophase 1 of meiosis; associated with the breaking and rejoining of the broken ends of different chromatids

Chitin

(Gr. chiton, a coat of mail) a polymer in which the monomer unit is the modified sugar N-acetyl glucosamine; the principal stiffening material in cell walls of true fungi and the exoskeleton of insects and crustaceans

Chlorenchyma

(Gr. chloros, green + enchyma, a suffix meaning tissue) parenchyma tissue possessing chloroplasts

Chlorosis

(Gr. chloros, green + osis, diseased state) failure of chlorophyll development, because of a nutritional disturbance or because of an infection of virus, bacteria, or fungus

Chlorophyll

(Gr. chloros, green + phyllon, leaf) the green pigment found in the chloroplast, important in the absorption of light energy in photosynthesis

Chlorophytes

(Gr. chloros, green + phyton, a plant) a group of mainly freshwater, photosynthetic protists commonly called green algae; they share several complex chemicals with land plants, and in this text they are classified as plants

Chloroplast

(Gr. chloros, green + plastos, formed) specialized cytoplasmic body, containing chlorophyll, in which occur the reactions of photosynthesis, including sugar and starch synthesis

Chromoplast

(Gr. chroma, color + plastos, formed) specialized plastid containing yellow or orange pigments

Endodermis

(Gr. endon, within + derma, skin) the layer of living cells, with thickened walls (Casparian strips) and no intercellular spaces, which surrounds the vascular tissue of certain plants and occurs in roots; the innermost layer of the cortex in roots

Endocarp

(Gr. endon, within + karpos, fruit) inner layer of fruit wall (pericarp)

Endomycorrhiza

(Gr. endon, within + mykos, fungus + riza, root) a mycorrhiza in which fungal hyphae grow between root cells and penetrate through some root cell walls to share the enclosed space with root cells

Endoplasmic reticulum

(Gr. endon, within + plasma, anything formed or molded; L. reticulum, a small net) originally, a cytoplasmic network adjacent to the nucleus; now, a system of closed tubules and flattened sacs in the cytoplasm of a eukaryotic cell; frequently abbreviated to ER

Endosperm

(Gr. endon, within + sperma, seed) the nutritive tissue formed within the embryo sac of seed plants; it often is consumed as the seed matures, but remains in the seeds of corn and other cereals

Endospore

(Gr. endon, within + spora, seed) a thick-walled resting spore, formed within the cells of certain bacteria after a complex process of nuclear division and cytoplasmic reorganization

Endosymbiosis

(Gr. endon, within + symbiosis) a symbiotic relationship in which cells of one species live within cells of another species

Ephemeral

(Gr. ephemeros, daily) an herbaceous plant whose life span is short, in general living for 6 or fewer months; often synonymous with "annual"

Epidermis

(Gr. epi, upon + derma, skin) a superficial layer of cells occurring on all parts of the primary plant body: stems, leaves, roots, flowers, fruits, and seeds; it is absent from the root cap and is not differentiated on the apical meristems

Epigeal

(Gr. epi, upon + ge, the earth) type of germination where cotyledons rise above the ground

Epigyny

(Gr. epi, upon + gyne, woman) the arrangement of floral parts in which the ovary is embedded in the receptacle so that the other parts appear to arise from the top of the ovary

Epicotyl

(Gr. epi, upon + kotyledon, a cup-shaped hollow) the upper portion of the axis of embryo or seedling, above the cotyledons

Epilimnion

(Gr. epi, upon + limne, marsh) an upper, aerated, warm zone of water that lies above a lower, less aerated, cold zone (the hypolimnion); common in large bodies of freshwater such as deep lakes

Epiphyte

(Gr. epi, upon + phyton, a plant) a plant that grows on another plant, yet is not parasitic

Enzyme

(Gr. ett, in + zyme, yeast) a protein that possesses a characteristic catalytic activity

Eusporangium

(Gr. eu, good or true + spora, seed + angeion, a vessel) the sporangium characteristic of all seedless vascular plants except for the true (leptosporangiate) ferns

Exocarp

(Gr. exo, without, outside + karpos, fruit) outermost layer of fruit wall (pericarp)

Gametangium

(Gr. gametes, a husband, gamete, a wife + angeion, a vessel) a cell or organ that produces gametes

Gamete

(Gr. gametes, a husband, gamete, a wife) a protoplast that fuses with another protoplast to form the zygote in the process of sexual reproduction

Genetics

(Gr. genesis, origin) the science of heredity

Gene

(Gr. genos, race, offspring) a group of base pairs in the DNA molecule in the chromosome that determines or conditions one or more hereditary characters

Genus (plural, genera)

(Gr. genos, race, stock) in the taxonomic hierarchy, a group of species

Glycogen

(Gr. glykys, sweet + gen, of a kind) a carbohydrate related to starch but found generally in the liver of animals

Glycolysis

(Gr. glykys, sweet + lysis, a loosening) the biochemical pathway affecting decomposition and oxidation of sugar compounds without involving free oxygen; early steps of respiration

Glucose

(Gr. glykys, sweet + ose, a suffix indicating a carbohydrate) a simple sugar, grape sugar, C6H12O6

Glyoxisome

(Gr. glykys, sweet + soma, body) a type of microbody that contains enzymes involved in the conversion of fats to carbohydrates during germination of fat-storing seeds

Gymnosperm

(Gr. gummos, naked + sperma, seed) seed plants that produce seeds that are exposed to the environment, rather than being enclosed in a fruit; the seeds may be located on the scales of cones or may be borne singly, covered with colorful aril tissue

Gynoecium

(Gr. gyne, woman + oikos, house) the aggregate of carpels in the flower of a seed plant

Haploid

(Gr. haploos, single + oides, like) having a single complete set of chromosomes, or referring to an individual or generation containing such a single set of chromosomes per cell; usually a gametophyte generation

Helix

(Gr. helix, anything twisted) anything having a spiral form; here, quite generally refers to the double spiral of the DNA molecule

Hemicellulose

(Gr. hemi, half + cellulose) a class of polysaccharides of the cell wall, built of several different kinds of simple sugars linked in various combinations

Hermaphrodite flower

(Gr. herinaphroditos, a person having the attributes of both sexes, represented by Hermes and Aphrodite) a flower having both stamens and pistils

Heteromorphic

(Gr. hetero, other + morphe, form) referring to organisms with sporic life cycles in which the sporophyte and gametophyte generations look different

Heterogamy

(Gr. heteros, different + gamos, union or reproduction) reproduction involving two types of gametes

Chrysophyta

(Gr. khrusos, gold) a small group of freshwater and (mainly) unicellular algae that contain chlorophylls a and c, have cellulose walls (sometimes with silica), and store carbohydrate as oil droplets; classified in this text with protists in the heterokont group

Kinetochore

(Gr. kinein, to move + chorein, to move apart) specialized component of a chromosome, connecting the centromere to spindle tubules during mitosis or meiosis

Cladode

(Gr. kladodes, having many shoots) a cladophyll

Cladophyll

(Gr. klados, a shoot + phyllon, leaf) stem or branch resembling a leaf

Cladogram

(Gr. klados, twig + gramma, letter) a diagram presenting a hypothesis on the sequence of branching events that occurred to generate a given set of presentday taxa from their common ancestor

Clade

(Gr. klados, twig) a branch in the tree of life, consisting of an originating taxon and all of its descendant taxa

Cladistics

(Gr. klados, twig) a set of quantitative methods and concepts for generating hypotheses about the evolutionary relationships among taxa; a form of systematics that shows evolutionary relationships among organisms by arranging them in a branching diagram (a cladogram), each branch representing organisms that share certain derived traits

Clone

(Gr. klon, a twig or slip) a group of genetically identical individual organisms produced asexually

Coenocytic

(Gr. koinos, shared in common + kytos, a vessel) a condition in which an organ or organism consists of a single cell with many nuclei, rather than being divided into many cells

Coleoptile

(Gr. koleos, sheath + ptilon, down, feather) the first leaf in germination of grasses that sheaths the succeeding leaves

Coleorhiza

(Gr. koleos, sheath + rhiza, root) sheath that surrounds the radicle of the grass embryo and through which the young root bursts

Collenchyma

(Gr. kolla, glue + enchyma, a suffix, derived from parenchyma and denoting a type of cell tissue) a tissue composed of living cells with thickened cell walls capable of stretching that fit rather closely together; found in young stems and petioles

Conidiosporangium

(Gr. konis, dust + sporangium) sporangium formed by being cut off from the end of a terminal or lateral hypha

Cone

(Gr. konos, a pine cone) a fruiting structure composed of modified leaves or branches, which bear sporangia (microsporangia, megasporangia, pollen sacs, or ovules), and frequently arranged in a spiral or four-ranked order; for example, a pine cone

Corm

(Gr. kormos, a trunk) a short, solid, vertical, enlarged underground stem in which food is stored

Cotyledon

(Gr. kotyledon, a cup-shaped hollow) seed leaf; there are two in the embryo/seedling of dicotyledonous plants; they generally store food and can expand and become photosynthetic; in monocotyledonous plants, only one is present, generally a digestive organ

Cycad

(Gr. kukas or koix, a kind of palm tree) a group of gymnosperms that are palmlike in appearance because of their large, evergreen, compound leaves and an absence of trunk branching; female cones are large and occur only at the tip of the trunk

Cyanobacteria

(Gr. kyanos, blue) a group of unicellular or filamentous photosynthetic prokaryotes also capable of fixing nitrogen; also called blue-green algae

Cyclosis

(Gr. kyklosis, circulation) movement of cytoplasm around a cell; synonym is cytoplasmic streaming

Cyme

(Gr. kyma, a wave, a swelling) a type of inflorescence in which the apex of the main stalk or the axis of the inflorescence ceases to grow quite early, relative to the laterals

Cystocarp

(Gr. kystos, bladder + karpos, fruit) a peculiar diploid spore-bearing structure formed after fertilization in certain red algae

Cytokinesis

(Gr. kytos, a hollow vessel + kinesis, motion) division of cytoplasmic constituents at cell division

Cytoplasm

(Gr. kytos, a hollow vessel + plasma, form) all the protoplasm of a protoplast outside the nucleus

Cytochrome

(Gr. kytos, a receptacle or cell + chroma, color) a class of several electron-transport proteins serving as carriers in mitochondrial oxidations and in photosynthetic electron transport

Cytokinin

(Gr. kytos, a receptacle or cell + kinetos, to move) a class of growth hormones important in regulation of cell division, delaying senescence, and organ initiation

Lamella (plural, lamellae)

(Gr. lamin, a thin blade) cellular membranes, frequently those seen in chloroplasts

Lichen

(Gr. leichen, thallus plants growing on rocks and trees) a composite organism consisting of a fungus living symbiotically with an alga

Lepidodendrids

(Gr. lepis, scale + dendron, tree) now extinct trees with trunks characteristically covered by diamond-shaped pads (scales) where leaves had been attached; early vascular plants related to living lycophytes such as the club moss Lycopodium

Leptosporangium

(Gr. leptos, fine, thin + spora, seed + angeion, a vessel) the sporangium characteristic of true ferns, originating from a single leaf cell and having a long, thin stalk, a one-cell-layer-thick wall, and an annulus that aids in spore dispersal

Leptoid

(Gr. leptos, small, thin + eidos, a shape) a sugarconducting cell found in some mosses

Leucoplast

(Gr. leuk-, white + plastid) a colorless plastid

Lipid

(Gr. lipos, fat + L. ides, suffix meaning son of; now used in sense of having the quality of) any of a group of fats or fatlike compounds insoluble in water and soluble in fat solvents

Lobed leaf

(Gr. lobos, lower part of the ear) a leaf divided by clefts or sinuses

Parenchyma

(Gr. parenchein, an ancient Greek medical term meaning to pour beside and expressing the ancient concept that the liver and other internal organs were formed by blood diffusing through the blood vessels and coagulating, thus designating ground tissue) a tissue composed of cells that perform housekeeping functions such as photosynthesis and storage of water and other substances; cells usually have thin walls of cellulose, and often fit rather loosely together, leaving intercellular spaces

Parthenogenesis

(Gr. parthenos, virgin + genesis, origin) the development of a gamete into a new individual without fertilization

Parthenocarpy

(Gr. parthenos, virgin + karpos, fruit) the development of fruit without fertilization

Pathogen

(Gr. pathos, suffering + genesis, beginning) an organism that causes a disease

Pathology

(Gr. pathos, suffering + logos, account) the study of diseases, their effects on plants or animals, and their treatment

Pectin

(Gr. pektos, congealed) a water-soluble polysaccharide, a component of cell walls and the middle lamella between cells; the basis of fruit jellies

Pentose

(Gr. pente, five + ose, a suffix indicating a carbohydrate) a five-carbon atom sugar

Peptide

(Gr. pepton, cooked or digested, a substance remaining after the digestion of proteins) two or more amino acids linked end to end

Peristome

(Gr. peri, about + stoma, a mouth) in mosses, a fringe of teeth about the opening of the sporangium

Perianth

(Gr. peri, around + anthos, flower) the petals and sepals taken together

Periderm

(Gr. peri, around + derma, skin) protective tissue that replaces the epidermis after secondary growth is initiated; consists of cork, cork cambium, and phelloderm

Pericarp

(Gr. peri, around + karpos, fruit) fruit wall, developed from the ovary wall

Pericycle

(Gr. peri, around + kyklos, circle) root tissue bound externally by the endodermis and internally by the xylem and phloem; site of initiation of lateral roots, cork cambium, and portions of the vascular cambium in some roots

Perithecium

(Gr. peri, around + theke, a box) a flaskshaped ascoma that opens at the narrow end to release ascospores

Petal

(Gr. petalon, a flower leaf) one of the flower parts, usually conspicuously colored

Phage

(Gr. phago to eat) a virus-infecting bacteria; originally bacteriophage

Phenotype

(Gr. phaneros, showing + type) the external visible appearance of an organism

Phelloderm

(Gr. phellos, cork + derma, skin) a layer of cells formed in the stems and roots of some plants from the inner cells of the cork cambium

Phellogen

(Gr. phellos, cork + genesis, birth) cork cambium, a cambium giving rise externally to cork and in some plants internally to phelloderm

Phellem

(Gr. phellos, cork) outer layers of the periderm consisting of dead cells formed by the phellogen; sometimes called cork

Phloem

(Gr. phooos, bark) food-conducting tissue, consisting of sieve-tube members with companion cells or sieve cells, phloem parenchyma, and fibers

Forb

(Gr. phorbe, fodder or pherbein, to graze) an herbaceous plant that is neither a grass nor a grasslike relative

Photoautotroph

(Gr. photos, light + autos, self + trophein, to feed) an organism that uses light as an energy source and CO2 as a carbon source

Photoheterotroph

(Gr. photos, light + heteros, other + trophein, to feed) an organism that uses light as an energy source and various organic compounds as a carbon source

Photoperiod

(Gr. photos, light + period) the optimum length of day or period of daily illumination required for the normal growth and maturity of a plant

Photosynthesis

(Gr. photos, light + syn, together + tithenai, to place) a process in which carbon dioxide and water are brought together chemically to form a carbohydrate, the energy for the process being radiant energy

Phototroph

(Gr. photos, light + trophein, to feed) an organism that derives energy from light

Phototropism

(Gr. photos, light + tropos, turning) a growth curvature in which light is the stimulus

Phreatophyte

(Gr. phrear, a well + phuton, plant) a tree or shrub that grows with its roots in continuous contact with ground water

Physiognomy

(Gr. phusis, nature + gnomon, judge) originally, the art of judging human character from facial features; in plant ecology it is the structure, or architecture, of a vegetation type or a plant community

Phytoplankter

(Gr. phuto, plant + plankter, wanderer) a photosynthetic organism (generally single-celled) that is part of the plankton, a body of floating cells near the surface of fresh or saline bodies of water

Phycobilisomes

(Gr. phykos, seaweed + L. bilis, relating to greenish bile + Gr. soma, body) rods or discs of accessory pigments that are attached to photosynthetic membranes in cyanobacteria; they absorb light in the green to orange part of the spectrum

Phycobiont

(Gr. phykos, seaweed + bios, life) the algal partner in a lichen

Phycoerythrin

(Gr. phykos, seaweed + erythros, red) a red phycobilin pigment occurring in red algae

Phycocyanin

(Gr. phykos, seaweed + kyanos, blue) a blue phycobilin pigment occurring in cyanobacteria

Phycology

(Gr. phykos, seaweed + logos, word, thought) the science of the study of algae

Sphenophytes

(Gr. sphen, wedge) synonymous with horsetails; until recently, horsetails were classified in their own division, the Sphenophyta, but in this text they are classified as monilophytes, together with whisk ferns, ophioglossalean ferns, marattialean ferns, and true ferns

Spodosol

(Gr. spodos, wood ashes; R. pod, under + zola, ashes) one of the 10 world soil orders, characterized by an ashy, sandy, bleached acidic A2 horizon and associated mainly with coniferous forest vegetation; synonymous with podzol

Spore

(Gr. spora, seed) a one-celled or few-celled reproductive unit that develops into a multicellular organism without first fusing with another reproductive unit; contrast with seed and gamete

Stele

(Gr. stele, a post) the central vascular cylinder, inside the cortex, of roots and stems of vascular plants

Stereid

(Gr. stereos, solid) thick-walled cells at or near the epidermis of certain mosses

Sterigma (plural, sterigmata)

(Gr. sterigma, a prop) a projection from a basidium that extrudes a basidiospore at its tip and assists in ballistospore release

Stoma (plural, stomata)

(Gr. stoma, mouth) a minute opening plus two guard cells in the epidermis of leaves and stems, through which gases pass

Strobilus

(Gr. strobilos, a cone) a number of modified leaves (sporophylls) or ovule-bearing scales grouped together on an axis

Stroma

(Gr. stroma, a bed or matress) the proteinaceous solution in the central region of chloroplasts, the location of the reactions of the carbon cycle of photosynthesis

Style

(Gr. stylos, a column) slender column of tissue that arises from the top of the ovary and through which the pollen tube grows

Symplast

(Gr. syn, together + plastides, formed) the region of a plant tissue inside of the plasma membrane of the cells that form it, especially when the cell interiors are connected by plasmodesmata; contrast to Apoplast

Synandry

(Gr. syn, with + andros, a man) a condition in which stamens are united

Symbiotic relationship

(Gr. syn, with + bios, life) a prolonged close association of two or more kinds of organisms, also called symbiosis; see also mutualism and parasitism

Syncarpy

(Gr. syn, with + karpos, fruit) a condition in which carpels are united

Sympetaly

(Gr. syn, with + petalon, leaf) a condition in which petals are united

Synsepaly

(Gr. syn, with + sepals) a condition in which sepals are united

Synergids

(Gr. synergos, toiling together) the two cells at the micropylar end of the embryo sac, which, with the third (the egg), constitute the egg apparatus

Tapetum

(Gr. tapes, a carpet) nutritive tissue in the sporangium, particularly an anther

Taxon (plural, taxa)

(Gr. taxis, order) a general term for any taxonomic rank; for example, species, orders, and kingdoms are taxa

Technology

(Gr. techne, skill + logos, reason) a body of knowledge applied to industrial or commercial objectives

Telophase

(Gr. telos, completion + phase) the last stage of mitosis, in which daughter nuclei are reorganized

Teliospore

(Gr. telos, completion + spore) a dikaryotic basidiomycete spore that is adapted to survive through winter and to produce basidiospores thereafter

Tetraploid

(Gr. tetra, four + ploos, fold) having four sets of chromosomes per nucleus

Tetrad

(Gr. tetradeion, a set of four) a group of four, usually referring to the meiospores immediately after meiosis

Thallophytes

(Gr. thallos, a sprout + phyton, plant) all plants whose body is a thallus, that is, lacking roots, stems, and leaves: algae, fungi, liverworts

Thallus (plural, thalli)

(Gr. thallos, a sprout) a plant, fungus, or protist body that is simpler than a vascular plant, lacking lignified vascular tissue, and therefore lacking roots, leaves, and stems

Thermocline

(Gr. therme, heat + klino, slope) a zone of rapidly changing temperature that separates the epilimnion from the hypolimnion in large bodies of freshwater

Thermoperiod

(Gr. therme, heat + periodos, circuit) the difference, in degrees, between the greatest and lowest temperatures experienced at one location within a 24- hour period

Thylakoid

(Gr. thylakos, sack + N.L. oid, a thing that is like) the inner membranes of the chloroplasts

Tonoplast

(Gr. tonos, stretching tension + plastos, molded, formed) the cytoplasmic membrane bordering the vacuole; so-called by de Vries, as he thought it regulated the pressure exerted by the cell sap

Tracheophytes

(Gr. tracheia, windpipe + phyton, plant) vascular plants

Tracheid

(Gr. tracheia, windpipe) an elongated, tapering xylem cell with lignified pitted walls, adapted for conduction and support, and without open end walls

Triose

(Gr. treis, three + ose, suffix indicating a carbohydrate) any three-carbon sugar

Trisomic

(Gr. treis, three + soma, body) a plant containing one additional chromosome, 2n + 1

Trichome

(Gr. trichoma, a growth of hair) a short filament of one or more cells extending from the epidermis

Trichogyne

(Gr. trichos, a hair + gyne, female) receptive hairlike extension of the female gametangium in the Rhodophyta and Ascomycetes

Tropism

(Gr. trope, a turning) movement or curvature caused by an external stimulus that determines the direction of movement

Vegetation

(L. vegetare, to quicken) the plant cover that clothes a region; it is formed of the species that make up the flora, but is characterized by the abundance and life form (tree, shrub, herb, evergreen, deciduous plant, and so on) of certain of them

Vector

(L. vehere, to carry) an organism, usually an insect, that carries and transmits disease-causing organisms; a DNA molecule used to transmit genes in a transformation procedure

Venation

(L. vena, a vein) arrangement of veins in a leaf blade

Venter

(L. venter, the belly) enlarged basal portion of an archegonium in which the egg cell is borne

Ventral suture

(L. ventralis, pertaining to the belly) the line of union of the two edges of a carpel

Vesicle

(L. vesicula, small bladder) a small, membraneenclosed cavity in the cytoplasm of a cell

Vibrio

(L. vibrare, to shake, vibrate) a genus of short, rigid motile bacteria having one or more polar flagella, being typically shaped like a comma or an S

Vine

(L. vinea, of wine) a woody plant with a flexible stem that is supported by trailing along the ground or by climbing upward on a shrub, tree trunk, or some other surface

Virulence

(L. virulentia, a stench) the relative infectiousness of a bacteria or virus, or its ability to overcome the resistance of the host metabolism

Virion

(L. virulentus, full of poison) infectious virus particle as it exists outside a host

Virus

(L. virus, a poisonous or slimy liquid) a disease principle that can be cultivated only in living tissues, or in freshly prepared tissue brei

Volva

(L. volva, a wrapper) cup at base of stipe or stalk of a basidiomycete fruiting body

Involucre

(L.involucrum, a wrapper) a whorl or rosette of bracts surrounding an inflorescence

Locule

(L.loculus, dim. of locus, a place) a cavity of the ovary in which ovules occur

Valve

(L.valva, door) openings in bryophyte capsules that allow spores to be dispersed

Tundra

(Lapp, tundar, hill) meadowlike vegetation at low elevation in cold regions that do not experience a single month with average daily maximum temperatures greater than 50°F

Peat

(M.E. Pete, of Celtic origin, a piece of turf used as fuel) any mass of semicarbonized vegetable tissue formed by partial decomposition in water

Advanced

(M.E. advaunce, to forward) said of a taxonomic trait thought to have evolved late in time from some more primitive trait

Bud

(M.E. budde, bud) an undeveloped shoot, largely meristematic tissue, generally protected by modified scale-leaves; also a swelling on a yeast cell that will become a new yeast cell when released

Kelp

(M.E. culp, seaweed) a collective name for any of the large brown algae

Gill

(M.E. gile, a lip, probably because of its resemblance in shape and arrangement to gills of fishes) in certain basidiomata, thin, spore-bearing plates on the underside of the cap

Meadow

(M.E. medoue) a vegetation type dominated by herbaceous plants, including forbs and grasses, but occupying a habitat and climate normally capable of supporting forest vegetation

Desert shrub

(M.E. schrubbe, shrub) a vegetation type characterized by evergreen or drought-deciduous shrubs growing together rather openly, generally in an area with annual precipitation less than 25 cm

Solution

(M.E. solucion, from O.T. solucion, to loosen) a homogeneous mixture, the molecules of the dissolved substance (for example, sugar), the solute, being dispersed between the molecules of the solvent (for example, water)

Starch

(M.E. sterchen, to stiffen) a complex insoluble carbohydrate, the chief food storage substance of plants, that is composed of several hundred hexose sugar units and that easily breaks down on hydrolysis into these separate units

Tree

(M.E. treow) a woody plant having a single trunk

Wood

(M.E. wode, wude, a tree) a dense growth of trees, or a piece of a tree, generally the xylem

Shrub

(M.E., schrubbe) a woody plant arising from many stems, as opposed to a tree, which has a single stem (trunk)

Compound

(M.F. compondre, put together) a chemically distinct substance produced by the union of two or more elements in definite proportion by weight; formed from specific molecules

Anther

(M.L. anthera- from the Gr. anthros, meaning flower) pollen-bearing portion of stamen

Aril

(M.L. arillus, a wrapper for a seed) an accessory seed covering formed by an outgrowth at the base of the ovule in Taxus

Basidiomycota

(M.L. basidium, a little pedestal + Gr. mykes, fungus) a monophyletic phylum in kingdom Fungi, in which all members extrude meiospores from a basidium; mycelial members have septate hyphae, and a dikaryotic stage in the sexual life cycle

Basidiospore

(M.L. basidium, a little pedestal + spore) meiospore that is extruded from a basidium in basidiomycete fungi

Alcohol

(M.L. from Arabic al-kuhl, a powder for painting eyelids; later applied, in Europe, to distilled spirits that were unknown in Arabia) a product of the distillation of wine or malt; any one of a class of compounds analogous to common alcohol; the ending designates a member of this class of compounds

Metabolism

(M.L. from the Gr. metabolos, to change) the process, in an organism or a single cell, by which nutritive material is built up into living matter, or aids in building living matter, or by which protoplasm is broken down into simple substances to perform special functions

Haustorium (plural, haustoria)

(M.L. haustrum, a pump) a projection of fungal hyphae that acts as a penetrating and absorbing organ

Lenticel

(M.L. lenticella, a small lens) a structure of the bark that permits the passage of gas inward and outward

Sepals

(M.L. sepsium, a covering) outermost flower structures that usually enclose the other flower parts in the bud

Agar

(Malay agaragar) a gelatinous substance obtained mainly from certain species of red algae

Bladder

(O.E. bladre, a blister) a gas-filled sac with buoyancy that keeps some aquatic plants upright

Kingdom

(O.E. cyningdom, territory ruled by a king or queen) in the taxonomic hierarchy, a group of phyla or divisions

Foot

(O.E. fot, foot) that portion of the sporophyte of bryophytes and lower vascular plants that is sunk in gametophyte tissue and absorbs food parasitically from the gametophyte

Girdle

(O.E. gyrdel, enclosure, girdle) that region of a stem from which a ring of bark extending to the cambium has been removed

Loam

(O.E. lam or Old Teutonic lai, to be sticky, clayey) a particular soil texture class, referring to a soil having 30% to 50% sand, 30% to 40% silt, and 10% to 25% clay

Leaf

(O.E. leaf) lateral outgrowth of stem axis, which is the usual primary photosynthetic organ, and in the axil of which may be a bud

Stem

(O.E. stemn) the main body of the portion aboveground of tree, shrub, herb, or other plant; the ascend ing axis, whether aboveground or belowground, of a plant, in contradistinction to the descending axis or root

Tiller

(O.E. telga, a branch) a grass stem arising from a lateral bud at a basal node; tillering is the process of tiller formation

Inheritance

(O.F. enheritance, inheritance) the reception or acquisition of characters or qualities by transmission from parent to offspring

Pioneer

(O.F. pionier, a foot soldier sent out to clear the way) in succession, an organism capable of occupying newly exposed land or land that has been cleared of previous vegetation by some catastrophic disturbance; generally an r-selected species

Steppe

(R. step, a lowland) a vegetation type in which shrubs are intermixed with perennial grasses in a semiarid region; sometimes defined as a vegetation type dominated by relatively short, perennial grasses without any woody vegetation

Chaparral

(Sp. chaparro, low, woody vegetation) a vegetation type characterized by small-leaved, evergreen shrubs growing together into a nearly impenetrable scrub

Savannah

(Sp. sabana, a large plain) vegetation of scattered trees in a grassland matrix; originally limited to tropical regions

Bark

(Swedish bark, rind) the external group of tissues, from the cambium outward, of a woody stem or root

Taiga

(Teleut, taiga, rocky mountainous terrain) a broad northern belt of vegetation dominated by conifers; also, a similar belt in the mountains just below alpine vegetation

Gram's stain

(after Hans C. M. Gram) a method for the differential staining of bacteria; distinguishes species on the basis of cell wall composition, which determines whether stain is retained

Cellulose

(cell + ose, a suffix indicating a carbohydrate) a complex carbohydrate occurring in the cell walls of the majority of plants; it is composed of hundreds of simple sugar molecules, glucose, linked together in a characteristic manner; cotton fibers are largely cellulose

Carbohydrate

(chemical combining forms, carbo, carbon + hydrate, containing water) a food composed of carbon, hydrogen, and oxygen, with the general formula CnH2nOn

Chromatid

(chromosome + L. id, suffix meaning daughters of) the half chromosome during prophase and metaphase of mitosis, and between prophase I and anaphase II of meiosis

Catkin

(literally a kitten, apparently first used in 1578 to describe the inflorescence of the pussy willow) a type of inflorescence, really a spike, generally bearing only pistillate flowers or only staminate flowers, which eventually fall from the plant entirely

Liverwort

(liver + M.E. zuort, a plant; literally, a liver plant, so named in medieval times because of its fancied resemblance to the lobes of the liver) common name for the class Hepaticae of the Bryophyta

Meiocyte

(meiosis + Gr. kytos, currently meaning a cell) any cell in which meiosis occurs

Meiospores

(meiosis + spores) haploid spores made to disperse the recombinant nuclei that result from meiosis

Meristoderm

(meristem + epidermis) the outer meristematic cell layer (epidermis) of some Phaeophyta

Mitospore

(mitosis + spore) a spore that bears the same genotype as the parental organism because its nucleus was made by mitotic division of a parental nucleus; often functions in asexual reproduction

Alga

(plural, algae) (L. alga, seaweed) informal name for a large group of species of simple, photosynthetic, mainly aquatic plants that lack vascular tissue (and therefore lack true stems, leaves, and roots); in this textbook, some algal groups (green, red) are classified in the plant kingdom, whereas most (brown, golden, diatoms) are classified as protists

Antheridium

(plural, antheridia) (anther + Gr. idion, dim. ending, thus a little anther) in plants, the male gametangium or sperm-bearing organ of plants other than seed plants; in ascomycete fungi, a specialized hyphal tip that fuses with an ascogonium to deliver gamete nuclei

Ascogonium

(plural, ascogonia) in ascomycete fungi, an enlarged hyphal tip that accepts gamete nuclei from an antheridium and initiates the dikaryotic stage of the sexual life cycle

Ascoma

(plural, ascomata) a sexual fruiting body made by an ascomycete fungus

Basidium

(plural, basidia) (M.L. basidium, a little pedestal) a thickened, club-shaped or elongate cell that extrudes meiospores in basidiomycete fungi

Basidioma

(plural, basidiomata) a sexual fruiting body of a basidiomycete fungus, composed of branching dikaryotic hyphae, basidia, and basidiospores

Cleistothecium

(plural, cleistothecia) (Gr. kleistos, closed + thekion, a small receptacle) a closed spherical ascoma

Coccus

(plural, cocci) (Gr. kokkos, a berry) a spherical bacterium

Conidium

(plural, conidia) (Gr. konis, dust) mitospores of fungi that form individually (not in a sporangium) by releasing parts of a hypha; conidia may arise by fragmentation of a hypha or by releasing cells from the tip of a hypha

Pinna

(plural, pinnae) (L. pinna, a feather) leaflet or division of a compound leaf (frond)

Protease

(protein + ase, a suffix indicating an enzyme) an enzyme breaking down a protein

Redox reaction

(reduction + oxidation) a chemical reaction in which one or more reactants is reduced (gains electrons) and one or more reactants is oxidized (loses electrons)

Ribosomes

(ribo, from RNA + Gr. somatos, body) small particles 10 to 20 nm in diameter, containing RNA and proteins and involved in the synthesis of proteins

Smog

(sm from smoke + og from fog) polluted air containing volatile and particulate hydrocarbons, oxides of sul fur and/or nitrogen, and ozone; brown-tinted and less transparent than clean air

Sporangiophore

(sporangium + Gr. phorein, to bear) a hypha that bears one or more sporangia

Sporangium (plural, sporangia)

(spore + Gr. angeion, a vessel) a single cell or multicellular enclosure in which spores are made

Sporophyll

(spore + Gr. phyllon, leaf) a spore-bearing leaf

Sporophyte

(spore + Gr. phyton, a plant) in alternation of generations, the plant in which meiosis occurs and which thus produces meiospores

Tetrasporine line

(tetraspore + L. ine, suffix meaning like) a line of evolutionary development in the algae in which mitosis is directly followed by cytokinesis, resulting in a filament, thallus, or complex plant body of varied form

rDNA

DNA that specifies the structure of the RNA molecules found in ribosomes

Biological barrier

a barrier to crossing (hybridization) of plants caused by differences in pollination vector or timing in flower opening, in contrast to physiologic barriers (incompatibility of pollen with stigma or style) or ecologic barriers (habitats too far apart)

Coral fungus

a basidiomycete fungus in which the basidioma resembles a marine coral

Bird's nest fungus

a basidiomycete that makes a basidioma resembling a miniature nest with eggs

Inclusion body

a body found in the cells of organisms with a virus infection

Phragmoplast

a body, consisting of microtubules and vesicles, involved in the synthesis of the cell plate during cytokinesis of plant cells

Terminal bud

a bud at the end of a stem

Mixed bud

a bud containing both rudimentary leaves and flowers

Axillary bud

a bud formed in the axil of a leaf

Accessory bud

a bud located above or on either side of the main axillary bud

Naked bud

a bud not protected by bud scales

Lateral bud

a bud that grows out of the side of a stem

Tertiary consumer

a carnivore that eats other carnivores

Secondary consumer

a carnivorous animal that feeds on herbivorous animals (primary consumers)

Pollen sac

a cavity in the anther of a flowering plant, or a globose swelling attached to a cone scale in a conifer that initially contains diploid cells, each of which divides by meiosis and ultimately develops into a pollen grain

Sporocyte

a cell that will divide to generate spores

Ancestral character state

a character state that a clade inherited from its immediate ancestor; contrast with derived character state

Derived character state

a character state that evolved after the founding of a clade and was not present in the clade's immediate ancestor

Growth retardant

a chemical (such as cycocel, CCC) that selectively interferes with normal hormonal promotion of growth, but without appreciable toxic effects

Covalent bond

a chemical bond between two atoms formed by shared electrons, that is, electrons in bonding orbitals shared by the atoms

Ionic bond

a chemical bond formed between ions of opposite charge

Condensation reaction

a chemical or physical reaction from which one product is water

Absorptive nutrition

a feeding system characteristic of fungi, in which large molecules are broken into small molecules outside the feeder's body, and the small molecules are taken into the body one by one; contrast with ingestion of foods by animals

Molecular biology

a field of biology that emphasizes the interaction of biochemistry and genetics in the life of an organism

Ribose

a five-carbon sugar, a component of RNA

Phytoalexin

a flavonoid molecule that accumulates rapidly in a plant undergoing microbial attack; phytoalexins vary among plant families, but each is toxic to a broad spectrum of fungal and bacterial pathogens

Perfect flower

a flower having both stamens and pistils; hermaphroditic flower

Complete flower

a flower having four whorls of floral leaves: sepals, petals, stamens, and carpels

Pistillate flower

a flower having pistils but no stamens

Staminate flower

a flower having stamens but no pistils

Regular flower

a flower in which the corolla is made up of similarly shaped petals equally spaced and radiating from the center of the flower; star-shaped flower; actinomorphic flower

Imperfect flower

a flower lacking either stamens or pistils

Incomplete flower

a flower lacking one or more of the four kinds of flower parts

Yeast

a fungal body that consists of a single, rounded microscopic cell

Septate hypha

a fungal hypha that is divided into cell-like compartments by regularly spaced crosswalls (septa)

Shelf fungus

a fungus that forms a shelflike basidioma on wood

Mitosporic fungus

a fungus that has not been observed to reproduce sexually, but multiplies asexually by producing mitospores; previously called a deuteromycete or an imperfect fungus

Dry rot

a fungus, developing a fruit body at the source of its damp home, which is the cause of major decay in buildings causing extensive damage

Megagametophyte

a gametophyte that produces eggs; contrast to microgametophyte, which produces sperm cells

Survivorship curve

a graph relating age of organisms within a cohort (along the horizontal axis) to the proportion of organisms in that cohort still alive (along the vertical axis)

Absorption spectrum

a graph relating the absorption of a beam of light by a substance to the wavelength of the light

Electromagnetic energy spectrum

a graph showing the intensity of light (in energy units, for example, ergs or Joules) as a function of wavelength

Green algae

a group of (mainly freshwater) aquatic, simple plants lacking embryos and vascular tissue, but similar to more complex land plants by possessing starch, cellulose, and the same photosynthetic pigments; includes the charophytes, from which land plants are thought to have been derived

Root cap

a thimblelike mass of cells covering and protecting the apical meristems of a root; also site of gravity perception

Phosphoglyceric acid (PGA)

a three-carbon compound formed by the interaction of carbon dioxide (CO2) and a five-carbon compound, ribulose bisphosphate; the reaction yields two molecules of PGA for each molecule of the ribulose bisphosphate; the first step in the C3 carbon cycle of photosynthesis

Proton pump

a transmembrane enzyme that catalyzes the movement of protons from one side of the membrane to the other coupled to the expenditure of free energy (for example, hydrolysis of ATP); because energy is expended, protons can be transported against their concentration gradient

Pollen tube

a tube of cytoplasm that grows from the pollen grain through the pistil to an egg; it is the mature male gametophyte of flowering plants and contains only two sperm nuclei

Puffball

a type of basidioma consisting of a rounded mass of spore-producing cells surrounded (at least initially) by a leathery covering

Closed bundle

a vascular bundle lacking cambium

Grassland

a vegetation type dominated by herbaceous species, including forbs and grasses, and occupying an area too dry to support trees

Eastern deciduous forest

a vegetation type that includes a complex sequence of North American forest communities, all dominated by winter-deciduous trees, and occurring east of longitude 95°W and south of latitude 50°N

Woodland

a vegetation type with two canopy layers, a scattered overstory of trees that collectively shade less than 60% of the understory (but at least 30%), and a nearly continuous understory of forbs and grasses

Arctic zone

a vegetational or climatic zone at high latitudes, where conditions during the growing season are too cool for trees to exist

Pollination drop

a viscous, sticky fluid that exudes out through the micropyle of a gymnosperm ovule, to which pollen grains may adhere and be drawn back through the micropyle as the pollination drop dries and shrinks, or is reabsorbed by tissue within the ovule

Hydrophobin

a water-repellant protein secreted by certain lichen fungi

Tidal wetland

a wetland close enough to a maritime coastline to be influenced by tidal fluctuations, so that at some daily or seasonal times the wetland is submerged and at other times is exposed; also called a salt marsh, and dominated by perennial, succulent forbs and salttolerant grasses and sedges

Salt marsh

a wetland close enough to a maritime coastline to be influenced by tidal fluctuations, so that at some daily or seasonal times the wetland is submerged and at other times is exposed; dominated by perennial, succulent forbs and salt-tolerant grasses and sedges

Pfr and Pr

abbreviations for the far-red (FR) or red (R) absorbing form of phytochrome (P)

ABA

abscisic acid

Active solute uptake

accumulation of solutes in a cell by means of active transport

Ecosystem restoration

active management techniques used to reverse human-caused changes and to bring back the previous ecosystem

ADP

adenosine diphosphate

Seminal root

adventitious roots forming at the base of the seedling stem

Prop roots

adventitious roots from lower nodes of stems; act to support the shoot axis

Substomatal chamber

air space immediately below the stomatal pore; provides evaporative surfaces for transpiration

Root system

all of the roots and branches initially derived from the radicle of the embryo

Shoot system

all stems, leaves, buds, flowers, and fruits developed from the shoot apical meristem

Lateral root

branch roots initiated in the pericycle

Fibruous root system

branched root system lacking a clear, single primary root; common in grasses

Vascular cambium

cambium giving rise to secondary phloem and secondary xylem

Linked characters

characters of a plant or animal controlled by genes grouped together on the same chromosome

Root hairs

epidermal projections of root cells in region of maturation that increase the absorptive surface of the root

Marattialean ferns

eusporangiate ferns with upright stems and large leaves (fronds); not classified as true (leptosporangiate) ferns

Ophioglossalean ferns

eusporangiate ferns with upright stems and leaves divided into a narrow, fertile (sporebearing) part and a green, expanded part; not classified as true (leptosporangiate) ferns

Macroevolution

evolution that consists of changes large enough to represent the emergence of a new life form, such as evolution of flowering plants from mosslike ancestors

Microevolution

evolution that consists of changes too small to alter the fundamental nature of a species, such as alterations in flower color

Haptera (singular, hapteron)

finger-like, tubular projections that make up the holdfast of certain kelps

F1

first filial generation in a cross between any two parents

Irregular flower

flower parts arranged so that only one line can divide the flower into two equal halves or mirror images; zygomorphic flower

Ascogenous hyphae

hyphae arising from the ascogonium, after the formation of n + n paired nuclei; the hymenial layer of the ascocarp develops from the ascogenoushyphae

Cutinization

impregnation of cell wall with cutin

Temperate rain forest

in North America, a conifer forest that dominates a coastal strip of land from northern California to the Gulf of Alaska; also called the Pacific Northwest conifer forest

Outgroup

in a cladistic study, taxa that are not part of the ingroup but are included in the study to locate the root of the ingroup

Conserved sequence

in cladistics, a segment of DNA that has the same base sequence in many taxa

Vascular tissue system

includes the primary and secondary xylem and phloem

Coenomycetes

informal term for all true fungi that lack a dikaryotic stage and have aseptate hyphae

Dikaryomycetes

informal term for true fungi that have a dikaryotic stage in the sexual life cycle; hyphae of these fungi are septate

13C,14C

isotopes of carbon that have additional neutrons; only 14C is radioactive

Noncyclic electron transport

movement of electrons in thylakoid membranes through a pathway that oxidizes a substrate (for example, H2O, releasing O2) and reduces an intermediate (for example, NADP, producing NADPH); the movement is stimulated by light and also generates a chemiosmotic gradient that provides energy for the synthesis of ATP

Red algae

multicellular, (mostly) marine, warm-water algae, some of which are large and differentiated into seaweeds with holdfast, stipe, and blade regions; closely related to the green algae and included with them in the plant kingdom

Brown algae

multicellular, cool-water, marine algae; includes the large kelps; placed among other heterokont protists in this text; also classified in its own division, the Phaeophyta

K selection

natural selection that favors long-lived, latematuring individuals that devote a small fraction of their resources into reproduction; many tree species are K strategists

Directional selection

natural selection that favors phenotypes at one end of a population's range of variation, leading to new adaptations

r selection

natural selection that favors short-lived, earlymaturing individuals that devote a large fraction of their resources to reproduction; annual herbs are r strategists

Stabilizing selection

natural selection that favors the current range of phenotypic variation in a population, preventing or limiting evolutionary changes

Diversifying selection

natural selection that increases genetic variation in a population, caused by environmental factors that favor two or more distinct types in a population

Productivity

net biomass produced by green plants through the process of photosynthesis; usually expressed as a rate (for example, 300 kg/hectare per year)

Abiotic

nonliving components of the environment that influence plant life, such as wind pollination

Perisperm

nutritive tissue in a seed derived from the nucellus

Map distance

on a chromosome, the distance in crossover units between designated genes

Equilibrium paradigm

once a widely accepted view of natural vegetation, which held that natural disturbances were rare and that the landscape was largely composed of stands of stable, species-rich climax vegetation

Apicomplexa

one group of pathogenic protists in the alveolate clade; contains some organisms previously classified as protozoa, for example, Plasmodium, the cause of malaria

Tube cell

one of the cells of the pollen grain; directs the growth of the pollen tube

Seed coat

outer layers of a seed, derived from the integuments

Albuminous cell

parenchyma-like cell associated with sieve cells in the phloem of gymnosperms and some ferns

Sheath

part of a leaf that wraps around the stem, as in grasses

Region of maturation

part of the root tip basal to the elongation zone where root hairs form and cells reach maturity

Region of elongation

part of the root tip where cells are elongating

Cell differentiation

processes of cell growth and other changes in a cell that lead to it becoming specialized

Ecologic(al) services

products of ecosystems that sustain aquatic and terrestrial life, including the production of oxygen (through photosynthesis), the filtering of pollutants, and the stabilization of soil

Protein body

protein storage organelle in seeds, sometimes called aleurone grain

Channels

proteins in a biological membrane that allow specific molecules to cross the membrane

Achene

simple, dry, one-seeded indehiscent fruit, with seed attached to ovary wall at one point only

Simple leaf

single leaf blade; may be lobed or have seriated edges, but is not divided into leaflets

Silt

soil particles between 2 and 50 microns in diameter

Sand

soil particles between 50 and 2,000 microns in diameter

Clay

soil particles less than 2 microns in diameter, composed mainly of aluminum (Al), oxygen (O), and silicon (S)

Rhizosphere

soil zone immediately outside a root containing microorganisms

Geographic isolation

spatial separation that prevents individuals of two populations from meeting to exchange genes

Transfer cells

specialized cells modified by their cell wall projections that may facilitate short-distance transport

Sieve area

specialized portion of sieve cell and sieve-tube member cell walls containing a cluster of small pores where each pore is surrounded by a carbohydrate called callose

Sibling species

species morphologically nearly identical but incapable of producing fertile hybrids

Alternation of generations

the alternation of haploid (gametophytic) and diploid (sporophytic) phases in the life cycle of many organisms; the phases (generations) may be morphologically quite similar or very distinct, depending on the organism

Root-to-shoot biomass ratio

the amount of biomass a community has above- and below- ground

Crassulacean acid metabolism (CAM)

the biochemical pathways by which the succulent genus Crassula and other plants fix carbon at night and release it for photosynthesis during the day

Aerobic respiration

the biochemical pathways through which organic molecules (for example, carbohydrate) are converted into simpler components and oxidized using molecular oxygen as a terminal electron acceptor

Anaerobic respiration

the biochemical pathways through which organic molecules (for example, carbohydrate) are converted into simpler components in the absence of molecular oxygen

Alcoholic fermentation

the biochemical process by which organic molecules are used as substrates to produce alcohol (generally, ethanol)

Peptide bond

the bond between carbon and nitrogen that unites two amino acid residues in a polypeptide chain or protein

Phylogenetic systematics

the branch of systematics that strives for a taxonomic system based on phylogenetic relationships

Ecosystem services

the byproducts or consequences of biota (usually vegetation) to humans; for example, the removal of pollutants from air and water

Ventral canal cell

the cell just above the egg cell in the archegonium

Vascular cylinder

the central portion of a stem or root bounded by and including the pericycle

Polymerization

the chemical union of monomers, such as glucose, or nucleotides to form starch or nucleic acid

Intermediary metabolism

the collection of all the metabolic pathways in a cell

Chromosome set

the collection of different chromosomes within a cell; a diploid cell has two chromosome sets; a haploid cell has only one chromosome set

Quaternary structure

the combination and arrangement of separate polypeptide chains in a protein

Autotetraploidy

the condition in which the doubling of the chromosome number occurs in one cell or between cells on the same plant

Permanent wilting

the condition of wilting of a plant when it can no longer obtain moisture from the soil

Terminal electron transport chain

the cytochromes in mitochondria that transfer electrons from NADH or FADH2 to molecular oxygen

Biomass pyramid

the diagrammatic summary of biomass of each trophic level, starting with producer biomass on the bottom layer of the diagram and ending with tertiary consumers on the top layer; each higher layer is smaller than the one below, so that the combination of layers look like a stepped pyramid

Water potential

the difference between the activity of water molecules in pure distilled water or water- saturated air and the activity of water molecules in any other system; the activity of water molecules is negative in unsaturated air and in solutions

Polar transport

the directed movement within plants of compounds (usually hormones) predominantly in one direction; polar transport overcomes the tendency for diffusion in all directions

Systematics

the discovery and scientific study of biological diversity with the aim of organizing that diversity into a system of named groups that is easy to use, has predictive value, and reflects our understanding of the relationships between the organisms; systematics and taxonomy are closely related, and many scientists use the terms more or less interchangeably

Radioactive decay

the disintegration of the nucleus of an atom through the emission of a high-energy α or β particle

Biodiversity

the diversity of life forms found in a region; measures include the number of species and their relative abundance

Nuclear envelope

the double membrane surrounding the nucleus of a eukaryotic cell

Zosterophyllophyta

the earliest known members of the lycophyte line, which are now extinct; they lacked leaves and roots, and they branched dichotomously like the rhyniophytes; however, the sporangia were attached to stems in a lateral rather than terminal position

Carbon fixation

the enzymatic reaction in which CO2 is attached to a receiver compound such as ribulose bisphosphate, thereby adding to the supply of organic carbon; occurs chiefly in photosynthesis

Nitrate reduction

the enzymatic reaction that converts nitrate ion, NO3-, to nitrite ion, NO2-

Phosphoenolpyruvate carboxylase

the enzyme responsible for the fixation of inorganic CO2 into oxaloacetic acid in a dark reaction of the C4 photosynthesis cycle

Divergent evolution

the evolution of increasingly greater differences between two taxa, usually resulting from exposure to different selection pressures

Crossing-over

the exchange of corresponding segments between chromatids of homologous chromosomes

Embryo sac

the female gametophyte of the angiosperms; generally a seven-celled structure; the seven cells are two synergids, one egg cell, three antipodal cells (each with a single haploid nucleus), and one endosperm mother cell with two haploid nuclei

Pioneer community

the first stage of a succession

Primary wall

the first-formed cell wall layer

Cone scale

the flat, woody parts of pine cones that spiral out from the central axis and bear the ovules (and later seeds) on their upper surfaces; each is subtended by a sterile bract

DNA replication

the formation of a DNA molecule with the same sequence of nucleotides as that of a pre-existing (template) DNA molecule

Nutrient cycling

the phenomenon of mineral and organic nutrients being taken up by plants, passed on to herbivores and carnivores, and released once again into the soil or the air by decomposers; also the phenomenon of nutrient addition to biota by the weathering of rocks or the eruptions of volcanoes, and the removal of nutrients from biota through erosion and their ultimate deposition into deep-ocean sediments

Side chain

the portion of an amino acid attached to its amine-(alpha)carbon-carboxylic acid backbone; each type of amino acid has a different side chain

Binary fission

the process of diving in two; the reproductive process of single-celled prokaryotes

Abscission

the process of leaves separating from a stem

Nitrogen fixation

the process of reducing N2 gas into ammonia and incorporating it into the protoplast; accomplished only by certain prokaryotes

Replication

the production of a facsimile or a close copy; here used to indicate the production of a second molecule of DNA exactly like the first molecule

Inbreeding

the production of offspring that originated when the sperm and egg came from genetically similar or genetically identical plants

Outcrossing

the production of offspring that originates when the sperm and egg come from genetically different plants

Substrates

the reactants of an enzymatically catalyzed chemical reaction

Leaf gap

the region composed of parenchyma that is located in the primary vascular cylinder above the point of departure of the leaf vascular tissue

Nucleoid

the region in a bacterial cell containing the principal chromosome; differs from a eukaryotic nucleus in not being surrounded by a nuclear envelope

Periplasmic space

the region in gram-negative bacteria between the plasma membrane and the lipopolysaccharide layer

Centromere

the region of a chromosome that binds to the spindle during mitosis

Intertidal zone

the strip of coastal land that is alternately inundated and exposed as tides rise and fall

Double helix

the structure of a DNA molecule, consisting of two complementary polynucleotides chains wound around each other in a right-handed corkscrew shape

Secondary structure

the structure of a protein produced by the bending of its backbone into specific shapes (for example, alpha helix)

Plant morphology

the study of how a plant develops from a single cell into diverse tissues and organs and an array of outer surfaces and shapes

Plant ecology

the study of how the environment affects plant organisms

Plant biology

the study of plant and plantlike organisms; synonymous with botany

Plant systematics

the study of plant evolution and classification

Plant genetics

the study of plant heredity

Plant molecular biology

the study of the biology of a plant cell at the molecular level

Plant physiology

the study of the physical and chemical processes involved in the functioning of the plant

Species diversity

the sum of every species present in an area, each species being multiplied by its relative abundance; compare with species richness

Oxidative phosphorylation

the synthesis of ATP from ADP plus phosphate as a result of aerobic respiration

Hydrophobic bond

the tendency of hydrophobic molecules in an aqueous environment to stick together, occurring because of the high free energy required to force them into solution

Chemiosmotic theory

the theory that ATP is synthesized in photosynthesis and mitochondrial respiration using as a direct energy source the flow of protons across a membrane in response to a concentration gradient or electrical potential difference, the gradient and/or potential difference being formed during electron transport reactions within the membrane

Cell theory

the theory that states that the cell is the fundamental unit of living matter and that organisms are formed from one or more cells

Tertiary structure

the three-dimensional structure of a protein molecule, stabilized by interactions among the side chains of the polypeptide chain

Stroma lamellae

the thylakoid membranes in a chloroplast that are relatively dispersed; contrast to Grana

Diversity

the total number of species that occur in a given community or region

Primary pit field

thin areas of primary cell walls

Secondary tissue

those tissues, xylem, phloem, and periderm, that form from secondary meristems

Primary tissues

those tissues—epidermis, xylem, phloem, and ground tissues—that form from primary meristems

Secondary xylem

tissue formed by division of the vascular cambium, usually toward the inside of the organ

Secondary phloem

tissue formed by division of the vascular cambium, usually toward the outside of the organ

Ground tissue system

tissues of the plant body responsible for housekeeping functions, for example, storage, support, photosynthesis, and others; collenchyma, sclerenchyma, and parenchyma

Aerate

to supply or impregnate with common air, such as by bubbling air through a culture solution

Homologous traits

traits that evolved from the same ancestral trait; in cladistic terms, homologous traits are alternative states of the same character

Equatorial rain forest

vegetation with several tree strata; characteristic of warm, wet regions; synonymous with tropical rain forest

Equilibrium

two alleles for the same gene remaining indefinitely in the population at a fixed ratio, even if one allele is dominant over the other

Hesperidium

type of berry, such as lemons and oranges, with a thick rind

Pepo

type of berry; fruits of plants in the cucumber family

Subsidiary cell

type of epidermal cell in contact with guard cells on leaves

Parallel venation

type of venation in leaves in which the vascular bundles are parallel to each other

Euglenoids

typically freshwater, single-celled, protist organisms that lack a cell wall and move with the help of two flagella; about one third of all species (including those in the genus Euglena) are photosynthetic, but the majority ingest food

Eudicots

typically have net-veined leaves, flower parts in fours or fives, embryos with two cotyledons, sieve-tube members having plastids with starch grains, stem vascular bundles in a ring, stamens with slender filaments, and three-apertured (tricolpate) pollen.

Monocots

typically have parallel-veined leaves, flower parts in threes, embryos with a single cotyledon, sieve-tube members having plastids with protein crystals (lacking starch grains), scattered vascular bundles, and prominent adventitious roots

Blade

typically the thin, expanded portion of a leaf; in some algae, the leaflike frond

Pollination syndrome

unique flower and pollen traits that adapt a flower for pollination by a particular vector

Palisade mesophyll

usually on the upper (abaxial) surface of the leaf; helps to more efficiently absorb sunlight

Day-neutral plants

varieties of plants whose flowering does not depend on day length; contrast Long-day plants and Short-day plants

Fascicular cambium

vascular cambium within vascular bundles