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