Plant Bio Exam 1

differentiate gymnosperm leaves and angiosperm leaves

(gymnosperm = non-flowering plants) do NOT have needles and cones just abnormal leaf shapes angiosperm leaves: often open in the spring -the green, nitrogen-rich chlorophyll is degraded and the nutrients are reabsorbed before the leaves are dropped in the fall

recap of plant cell cycle

*G1 phase*: cell doubles in size; organelles, enzymes, and other molecules increase in number G1 checkpoint *S phase*: DNA replicated and associated proteins synthesized; two copies of cell's genetic information now exist *G2 phase*: structures required for cell division begin to assemble; chromosomes begin to condense G2 checkpoint *M phase*: the two sets of chromosomes are separated (mitosis) and the cell divides (cytokinesis)

what are the resulting tissues of meristems?

*apical meristems* (SAM and RAM): -primary or transitional meristem --> primary growth ---protoderm--> gives rise to epidermis ---ground meristem--> gives rise to ground tissue ---procambium--> gives rise to primary vascular tissue *lateral meristems* -vascular cambium (layer b/t primary xylem and phloem)--> secondary vascular tissue -cork cambium or phellogen--> periderm *intercalary meristems* (found in the nodes of grasses): -intercalated into every segment and is responsible for making THAT segment longer (picture on slide 22)

what are the two transport system for cell-to-cell communication

*apoplastic pathway*: through cell wall; can avoid having to enter the cell -PASSIVE; no ATP required but no control, just flowing *symplastic pathway*: through cytoplasm -filters what can and can't pass -ACTIVE; requires ATP

what's a major difference between dicot and monocot leaf anatomy?

*monocots* have stoma on BOTH top and bottom!! have an upper and lower epidermis with cuticle and the mesophyll layer sits in between -vascular bundle in the center -there is no differentiation of mesophyll into spongy and palisade parenchyma (=isobilateral or equifacial leaves)

describe the types of leaf venation

*parallel*: veins run roughly parallel to midrib -monocots *palmate*: veins arise from common point of origin at base of midrib (above petiole) *pinnate*: veins project laterally on either side of midrib palmate and pinnate occur in dicots

describe the lead structure

*petiole* = leaf stalk *blade* = flattened portion of leaf *stipules* = leaf-like tissue attached to base of petiole (DICOT)

describe cell-to-cell communication

*plasmodesmata*: perforated channels that run through the cell wall (singular: plasmodesma) -narrow, plasma membrane-lined channels traversed by desmotubule (modified ER tubule) -serve as pathways for transport of amino acids, sugars, and signaling molecules tiny perforations between cell walls -through this, one cell sends desmotubule so the membrane of one becomes attached to the membrane of the other

what part of the dicot embryo becomes the future shoot? what part becomes the embryonic root?

*plumule*: future shoot *radicle*: embryonic root

differentiate between primary and secondary growth in plants in general

*primary*: growth in length; apical meristems -tips of roots and shoots *secondary*: growth in width; lateral meristems -vascular cambium and cork cambium ---vascular cambium produces new cells in a cyclical pattern ---"wakes up" in the spring and makes new xylem and phloem ---ALWAYS more xylem than phloem in plants with secondary growth ---as the plant grows thicker, the secondary phloem (new) squishes the primary phloem (old) and mostly relies on the new phloem (essentially replaced) ---secondary xylem is added to the primary xylem with secondary growth LOOK AT DIAGRAM (lecture 3 slide 21) AND BE ABLE TO IDENTIFY PARTS

describe primary growth in an arabidopsis seedling

*root apical meristem*: in charge of growing downwards, deeper *shoot apical meristem*: growing taller, responsible for future flowers, etc.

differentiate between the appearance of vascular tissue in different parts of the plant

*root*: xylem in plus sign, phloem fills in corner *stem*: ring of bundles -xylem is ALWAYS towards the center -plants that live longer than one season and grow in thickness have a strip of cambium between the xylem and phloem ---responsible for secondary growth *leaves*: smaller bundles in a linear arrangement -leaves cannot grow in thickness so no cambium present (no secondary growth) -phloem comes toward the bottom, xylem towards the top

explain what parts of the mature plant are made by SAM and RAM

*shoot apical meristem* makes the stem, leaves, flowers, fruit, and seeds -above ground parts of the plant! *root apical meristem* makes the primary and lateral roots -below ground parts of the plant!

what are the types of leaves?

*simple*: blade not divided into smaller leaflets -blade consists of only one piece -petiole of a leaf is directly attached to the stem *compound*: blade divided into smaller parts that look like small leaves called *leaflets* (lack axillary buds) -stalk of leaflets called *petiolule* -outgrowth, usually in pairs, may be found at the base of the petiolule--called a *stipel* (secondary stipule) ---only petiole has stipule

give some examples of how plants produce compounds we use as medicines or drugs

-*willow* (Salix) bark as a source of aspirin (acetylsalicylic acid) (animals chew on willow bark when they don't feel well) -*foxglove* (Digitalis purpurea) as a source of digitalis (treatment for cardiac problems) -*pacific yew* (Taxus brevifolia) as a source of taxol (cytotoxic treatment for ovarian cancer) -*coffee* (Coffea arabica) and *tea* (Camellia sinensis) as sources of caffeine (stimulant)

describe the nucleolus

-a spherical structure inside the nucleus of eukaryotic cells -site of ribosomal RNA transcription and processing as well as ribosome assembly -assembly of the ribosomal subunits

describe phloem in detail

-bidirectional but "down" because taking sugars from leaves and transporting them into and around the plant -LIVING vascular tissue -serves as route for long distance signaling (superinformation highway) -photosynthesis produces simple sugars that are stored in the roots; phloem takes sugars to the roots -cells are called *sieve elements (SE)* ---two kinds: ---sieve cells (gymnosperms) ---sieve-tube elements (angiosperms) ---bigger cells within the phloem are sieve-tube elements ---also contain sclerenchyma and parenchyma (complex tissue!!) -transport in the phloem ---loading sugars is energetically expensive ---when loaded, water follows osmotically (what pushes the whole system) ---sugars are released into the sink tissues (sink can be roots or fruit!)

describe the ground tissue system

-cells packed very tightly -very consistent; looks the same all over -most of the photosynthesis happens here (VERY important)

describe xylem in detail

-conducts water and nutrients from roots to elsewhere in the plant -*non-living* at maturity ---again, starts as living just so it can differentiate -cells are termed *tracheary elements (TE)* ---two kinds: ---*tracheids* and *vessel elements* ---both types of cells are non-viable at maturity ---helical wall thickening offer more mechanical support -sclerenchymatic fibers and parenchyma are both present in xylem (complex tissue!!) -xylem cell types: ---wide vessel elements are good at transporting water ---thin: mechanical support; the bones of the plant -xylem cells form thickened rings of secondary wall tissues and then die, leaving behind a hallow, reinforced vessel ---cell wall: cellulose and lignin (lots of lignin in secondary growth) ---lignified xylem provides structural support for vascular plants ---thicker they get, locking themselves out from other cells ---this is why they die (programmed cell death) -vessel elements contain perforations ---NO cell walls between vessel elements -the structure of xylem cell walls prevents embolisms from spreading ---embolism = air bubble; very dangerous ---breaks cohesion of water so it can't continue flowing ---perforations allow the water to migrate past the now useless area by moving sideways into next door upward flow -the resulting "column" is termed *vessel* (think a stack of rigatoni pasta)

describe chloroplasts / plasmids in plants

-double-membrane envelope -stroma: large soluble interior -thylakoid membrane system (stacks of membranes) -intrathylakoid space or lumen forms of plastids: 1) *proplastids* -precursor of ALL plastids, found in meristems -equivalent to stem cells in animals 2) *etioplasts* -form in shoots of dark-grown plants, distinctive internal structures -pale yellow color of dark-grown plants is given by etioplasts 3) *chloroplasts* -in all green tissues -etioplasts turn into chloroplasts within hours when dark-grown plants are moved into sun (turn green) (can be induced by light stimulus) 4) *amyloplasts* -prominent in roots -store starch -colorless 5) *chromoplasts* -in mature fruit, lots of carotenoids, little chlorophyll -orange and red pigments -protecting from excess light (low photosynthetic capacity) -attract animals for seed dispersal

describe the smooth ER in plants

-forms an interconnected network of tubules, vesicles, and cisternae -involved in the synthesis of lipids, including oils, photolipids, and steroids -metabolism of carbohydrates, regulation of calcium concentration (important second messenger) -detoxification of drugs and poisons

describe the central vacuole of plants

-found inside of the cytoplasm -important to the structure of plants (turgor/rigidity accomplished based on the amount of water in the vacuole) -can take up to 80% of the cell -contains pigments which give plants color -stores water and nutrients to aid in growth -dictates the rigidity of a plant cell -vacuolar membrane = *tonoplasts* -waste products are moved into the vacuole and stored there indefinitely until the cell dies -also contains defense compounds!!

describe peroxisomes in plants

-function like lysosomes -"toxic waste removal system" of the cell -breaks down long chains of fatty acids in lipid metabolism -contains enzymes such as oxidases and catalases -oxidases neutralize free radicals, formed from normal cellular metabolism, that could destroy proteins or DNA if a build up occured -catalases break down poisons such as alcohol, formaldehyde, and phenols -increase in number when grown in soil containing toxins

lists the functions of the vacuole in plant cells

-maintain cell size by adjusting turgor pressure ---active transport by proteins in tonoplast, K+ ions ---supports integrity of the cell wall ---could occupy up to 90% of cell volume -pushes the chloroplasts closer to the cell wall ---bigger the vacuole, closer they get pushed towards cell wall bc limited space ---uses sunlight more efficiently -contributes to homeostasis by storage of enzymes ---keeps acidic internal pH ---also detoxes by capturing toxic compounds -sequesters materials that could harm the cell -autophagy ("self-easting"): vacuole digests the other organelles in the cell ---bursts and releases digestive enzymes that consumes the cell from the inside ---usually when the cell is starved or before cell death be able to name three characteristics of a plant vacuole on the exam

describe the secondary cell wall

-many plant cell walls deposit additional layers of cell wall -this happens on the *inner surface* of primary walls -next, primary walls fuse with each other, forming a structure termed *middle lamella* dead at maturity (I THINK, CHECK) -the secondary cell wall typically consists of three layers, termed S1, S2, and S3 ---the layers differ in orientation of their *cellulose microfibrils* ---S1 sits right inside the primary cell wall and S3 is at very center

plant cells have a single large vacuole; describe

-occupies large percentage of the cells volume -contains cytoplasmic strands for communication between remote cell areas

describe epidermis in detail

-outer covering (replaced by bark in woody plants) -*controls water loss and protects plant* -tightly packed and often coated with *waxy cuticle* ---waxy cuticle prevents water loss -may have outgrowths/projections of a cell called *trichomes* ---can secrete droplets of sticky substance to immobilize predators -may contain *guard cells* (regulation of stomata; gas exchange) ---two guard cells form a stoma ---open or close depending on how much water is in central vacuole ---stomata only on bottom-side of the leaf ---if they close due to environmental stress, not getting CO2 so can't photosynthesize...starve so they have to reopen eventually or they will die -root hairs are also part of the epidermis ---increase SA to optimize exchange of water and nutrients

why could we not live without plants?

-plants produce most of the oxygen we breathe -plants produce most of the chemically stored energy we consume as food and burn for fuel ---plants fix carbon dioxide into energy-rich molecules (sugars) we animals can use as food (photosynthesis) -plants produce an amazing assortment of useful chemicals ---vitamin A and C ---vanillin ---caffeine ---morphine

describe the mitochondria in plants

-produce the cell's supply of ATP -regulate cell metabolism and cell death -contain an independent genome -evolved from free-living microbes (alpha-proteobacteria); developed an endosymbiotic relationship in animal and plant cells ---more ancestral than animal mitochondria -----more DNA and noncoding DNA especially

describe the dermal tissue system

-protects from external environment (physical and immunology-based protection) -some amount of exchange

describe periderm in detail

-replaces epidermis in stems and roots undergoing secondary growth (secondary tissue) -complex tissue containing cork, cork cambium, and phelloderm ---cork is full of lipids so it seals plant completely ---cork cambium contains highly active stem-cell-like cells (stains very dark because metabolically active)

describe ribosomes and the rough ER

-ribosomes consist of RNA and proteins; they are responsible for assembling proteins; ribosomes may number in the millions -ribosomes are made of a large and small subunit and are synthesized by the nucleolus -ribosomes can be found attached to the rough ER or suspended in the cytosol -ribosomes help translate the transcribed message in mRNA into amino acids; amino acids are linked together by ribosomal RNA to form a polypeptide chain; polypeptide chains undergo several modifications before becoming fully functioning proteins -nuclear envelope and rough ER-->smooth ER all ONE system (seamless)

what are the functions of roots

-roots *anchor the plant* in the substratum or soil -roots *absorb water and dissolved nutrients* or solutes (nitrogen, phosphorous, magnesium, boron, etc.) needed for normal growth, development, photosynthesis, and reproduction -in some plants, roots have become *adapted* for specialized functions

describe the golgi apparatus in plants

-stack of membranes -due to its large size, it was one of the first organelles discovered (1897) -found in the cytoplasm and composed of stacks of membrane-bound structures called cisternae; each stack is polarized (cis and trans face; cis is proximal to center and trans faces the plasma membrane) -functions in packing proteins inside the cell before they are sent to their destination; particularly important in processing proteins for *secretion*; also important in protein glycosylation and synthesis of cell wall polysaccharides -sometimes called *post office of the cell* since it packages and labels items and sends them to different parts of the cell

why study plants?

-to learn more about the natural world -to help conserve endangered plants and threatened environments -to better harness the abilities of plants to provide us with food, medicines, and energy -studying plants informs us about our world ---cells were first observed in plants ---viruses were first purified from plants (very first virus identified in plants) ---Mendel's studies of peas revealed the laws of inheritance which help us understand human diseases such as sickle cell anemia and hemophilia, as well as countless other human diseases that have a genetic contribution -------Mendel's work laid the foundation for the science of *plant genetics* and *modern plant breeding*

describe the earliest stages of dicot embryo development

-two-cell stage (terminal and basal cell) -*pro-embryo* grows as both terminal and basal cells divide -basal cells gives rise to *suspensor*; function of suspensor is to anchor the embryo at *micropyle* (=the opening of ovule, entry way for pollen) -embryo passes through *globular, heart, and torpedo stages* -*heart stage*: first notion of two cotyledons; torpedo stage has two distinct cotyledons (=dicot)

provide examples of plant vacuoles in nature

-when cutting an onion, vacuoles are broken which releases enzymes and chemicals that form syn-propanethial-S-oxide which burns the eyes ---anti-herbivore response -central vacuoles of crystals idioblast cells store needle-like calcium oxalate crystals for plant defense, ejected at herbivores -many lead cells, like mesophyll, epidermis, and trichomes, collect excess Cd, Zn, and Ni in the central vacuole ---very toxic to plants and found in many post industrial soils

define and describe the different types of ground tissue

1. *parenchyma* -loosely packed (sometimes tightly packed but generally loose) -cell walls thin with regular shape -metabolically active! -can survive for more than a year ---if they do, make secondary cell walls but never grow thick enough to be isolated from other cells -totipotent cells are equivalent to stem cells; can differentiate into any cell type ---can reverse cell fate (wound healing, adventitious roots) -one specialized type are *transfer cells* involved in *solute movement* -*chlorenchyma* = parenchyma cells that contain chloroplasts -skull-like structures are NOT parenchyma; they're vascular bundles in monocot plants 2. *collenchyma* -alive, typically elongated cells -soft and unevenly thickened cell walls ---can thicken in different patterns -cell wall continues to thicken--support to the organ -frequently found as mechanical tissue beneath epidermis in non-woody plants ---allows the plant to be upright -in photo on slide 15, can tell top is collenchyma because thick cell walls and much smaller than parenchyma 3. *sclerenchyma* -very thick and lignified cell walls -DEAD AT MATURITY -starts out as something that looks like parenchyma then it differentiates -two kinds of cells: *fibers* and *sclereids* ---fibers are long slender cells occurring in bundles (economical importance--flax); cells longer than they are wide ---sclereids (aka stone cells) have variable shape, may be branched; cells as long as they are wide; very irregular shape -------pit (looks like line in cell wall) = former communication spot -------stone cells in pear fruit are sclereids WATCH VIDEO ON CANVAS (simple permanent tissues) ---both cell types have structural and mechanical functions ---difference in thickness and liveliness at maturity

name three plant-specific structures and describe

1. *phragmosome*: sheet of cytoplasm formed in plant cells PRIOR TO division (during telophase), penetrating the central vacuole; contains microtubules and actin filaments; later transforms into phragmoplast -plant nucleus can't divide with huge bubble in the middle so has to be broken up ---cell plate helps initial separation of daughter cells -strands of cytoplasm penetrate the vacuole -nucleus migrates to the center and is suspended by cytoplasmic strands -the phragmosome forms and later transforms into phragmoplast 2. *preprophase band*: aggregate of microtubules, helps orient the spindle -plant cells lack centrioles as typical microtubule organizing centers -linked to the nucleus by phragmosome microtubules -*marks the future division site* 3. *cell plate*: initial separation of daughter cells, callose-rich --> cellulose + matrix -phragmoplast serves as scaffolding for the cell plate assembly -during telophase, the cytokinetic phragmoplast expands centrifugally, leading the cell plate towards attachment sites previously established by the preprophase band

describe the steps transport in the phloem

1. sugars are loaded into the phloem by active transport 2. water moves in by osmosis 3. the fluid moves through the sieve elements under pressure, by bulk flow (like water in a hose) 4. sugars are released into the sink tissues 5. water follows by osmosis

what are the two results of cell expansion

DEPENDS ON CELLULOSE MICROFIBRIL ORIENTATION *spherical cells*: expansion equally in all directions -cellulose microfibrils in messy arrangement all over *elongated cells*: longitudinal expansion -cellulose microfibrils in parallel arrangement on all sides but messy arrangement on the top

what are genetically biofortified foods

GOOD GMOs that are saving lives -vitamin A enriched rice -Iron enriched rice -antioxidant rich tomatoes

(T/F) cells in the elongation zone are still undifferentiated

TRUE

(T/F) if a small plant only has two leaves, those are most likely cotyledons

TRUE

(T/F) all parts of the plant are made of the same tissues that are organized and specialized differently

TRUE tissue types: -*dermal*: outside of plant body (not all dermal tissues will be epidermis) -*vascular*: takes water and nutrients and transports to all parts of the plant -*ground or fundamental*: filler; everything in between dermal and vascular all of these tissues look different in different parts of the plant because different arrangements

(T/F) one of the functions of the shoot apical meristem is to make leaves

TRUE bonsai clippers are removing apical meristems to remove apical dominance -will stop growing tall and thin and will start making lateral branches

(T/F) non-vascular plants do not have leaves

TRUE; get water through absorption throughout the whole structure have leaf-life structures but no true leaves -contain chlorophyll and need very moist environments -some can hibernate when conditions are not good and come back when h2o returns

(T/F) mammalian embryonic polarization takes MUCH longer

TRUE; over three days after fertilization

(T/F) altering a single gene can increase plants' drought tolerance

TRUE; transgenic plants will still start to wilt after 20 days of drought, but they recover after re-watering

what two serious diseases currently threaten the world's food supply?

_Phytophthora infestans_, cause of potato late blight (Irish famine), has re-emerged as a threat -came back stronger with more virulence _Puccinia graminis tritici_, the wheat stem rust fungus, has developed into a highly aggressive form -a new, hgihly pathogenic strain emerged in Uganda, called Ug99 -most wheat has *no resistance* to this strain -winds currents are spreading spores -can lose up to 100% of wheat in areas that heavily rely on it -at this time, no one knows if resistant strains will be developed in time to avoid a major famine

as the world population grows and grows, why is it essential that we know everything we can about plants

a major objective of plant science is to *increase food production* -current estimates indicate that we need to increase production by 70% in the next 40 years malnutrition and hunger disproportionately kill children -in 2020, 70 million people worldwide died of starvation ---15 million of them were children under 5 years of age, of which 99% lived in low- or middle-income countries ---7 million children under the age of 5 die each year to *undernutrition* and related causes (vitamin and nutrient deficiencies) ---a lack of adequate vitamin A kills one million children a year Globally, more than one billion people per year are chronically hungry -more than two billion people per year are chronically anaemic due to iron deficiency

describe the lower surface of the leaf (underside)

also made of a layer of dermal tissue, but the cells are different *guard cells* allow gases to move in and out of the leaf -these cells have special pores called *stomata* ---stomata are connected to the open spaced in the mesophyll -transpiration happens through these pores -CO2 enters, H2O and O2 leave (transpiration = evaporation of water from the leaves) stomata apicher: size of opening -when vacuole has lots of water, both sides swell causing the opening to widen -when dehydrated, they flatten on top of one another

what is another name for the apical meristem?

apical dome -is usually convex or flat and the surface is smooth -VERY sensitive ---any damage and the plant cannot grow that's why it's covered by leaves for protection the tiny leaves that surround the meristem are called leaf primordia the SAM is VERY small, usually 0.1-1mm i diameter

what is something both plants and animals have, something plants have but animals do not, and something only animals have

both: mitochondria only plants: cell wall and oil bodies -cell wall is rigid for shape and support -oil bodies are not surrounded by any membrane, just little droplets of fat; found in seed with high oil contact plant cells do NOT have lysosomes -function of lysosomes is accomplished by peroxisomes

how can plant scientists contribute to the alleviation of hunger?

by developing plants that: -are drought or stress tolerant -require less fertilizer or water -are resistant to pathogens -are more nutritious plant growth is often limited by drought stress (physical or economic water scarcity) -and drought stress is compounded by increasing global temperatures -in warm regions, crop yield can drop ~3-5% with every 1 C increase in temperature -even mild drought stress reduces yields ---may not kill them but lower yields because ATP is being used for stress response rather than plant growth

what are lateral meristems?

cause secondary growth in woody plants brings about tree rings! -as new xylem is added to the old xylem, the older wood becomes darker and the newer wood is lighter -forms rings that you can count to age a tree the study of growth rings in wood is called *Dendrochronology* -can tell us a LOT about our world in the past! ---can measure amounts of C14 to C12 in the atmosphere in different years

describe the plant nucleus

consists of: -*cajal body* ---involved in splicing -*nucleolus* -*nuclear pores* ---shuttle -*nuclear envelope* ---aka karyolemma -houses DNA -site of RNA transcription -regulates metabolic functions -*totipotency* ---under control of the nucleus, a single cell can regenerate all of the organs and tissues of the plant from a single cell (different from animal nuclei)

describe dermal tissues

covers leaves, flowers, fruits and seeds, and young stems and roots 1. epidermis -primary tissue -EVERY plant has -seedling covered with after germination 2. periderm -secondary tissue ('bark') -only in plants that grow a long time -made of dead cells woody plants with leaves: leaves covered in epidermis, stem/trunk covered in periderm

describe the later stages of dicot embryonic development

development of the *plumule* (embryonic shoot) and the *radicle* (embryonic "root") -roots come first to anchor the plant and decide if environment is okay (plant doesn't want to waste energy on development if environment is not optimal) *hypocotyl*: part of embryo below the cotyledons; very thick and sturdy hook-like structure; breaks through the soil as a final check to see if conditions are good enough for the plant to start growing as the embryo matures, endosperm depletes and cotyledons swell with storage nutrients *the entire process is tightly controlled by many genes and hormones*

who is Norman Borlaug?

distinguished plant breeder that saved India from famine--bred a new wheat that survived better

below the cell division zone (apical meristem) is the ______; explain

elongation zone -no new cells made here, the existing cells are just elongated beyond the elongation zone is the differentiation zone where we start to see xylem, phloem, etc. -differentiation occurs here

what provides food to the embryo sac?

endosperm

describe the origin of leaves

flowers formed in the Cretaceous period ~130-140 million years ago -at some point before the cretaceous period they developed leaves primitive plants did NOT have leaves -_Cooksonia_ and _Rhynia_ lived about 400 million years ago -EVERY stem splits into two ---no real root early leaves were little more than flaps of tissue -_Lycopodium_ and _Selaginella_ have leaves that resemble the earliest leaves -LOTS of surface area because they need lots of absorption larger and more complex leaves evolved in ferns and seed plants -very efficient at exchange but not advanced at reproduction

define tissues and one way to classify

groups of cells with similar functions *simple tissues*--1 type of cell -ex. NEED EXAMPLE *complex tissues*--2 or more cell types -ex. ---xylem (contains sclerenchymatic fibers and parenchyma) ---phloem (sclerenchyma and parenchyma) ---periderm (cork, cork cambium, and phelloderm)

in seed plants, the shoot apical meristem is multicellular; explain

has three zones: central zone, peripheral zone, and rib meristem cells in the *central zone* are a pool of undifferentiated stem cells -constantly dividing cells = *initials* -after every division, one daughter cell remains in the meristem and the other one may divide further and differentiate -no other job but to make more cells cell sin the *peripheral zone* (surrounds the sides and just below the central zone) proliferate and differentiate into *lateral organs* (leaves and flowers) cell sin the *rib meristem* (below both the central and peripheral zones) proliferate and differentiate into the *stem* the cells located in these zones stain darker than the surrounding cells and are very small; they are mostly nuclei with little cytoplasm because they're new and dividing cells ("INITIALS")

What is the vicious cycle plant biologists are currently working to break? How do they break it?

heat and drought reduce plant yields --> more land must be cleared to grow more crops --> removing trees to make way for more crops puts more CO2 into the atmosphere (more CO2 = more heat trapped) --> by developing plants that: -are drought or stress tolerant -require less fertilizer or water -are resistant to pathogens -are more nutritious

how do monocots differ from dicots in leaf structure?

in some monocots: -petiole is lacking -the blade is supported by a flattened structure called the *leaf sheath* which clasps the stem ---IS photosynthetic ---(think of peeling off layers of grass when little)

where does dicot embryonic development occur?

in the flower (sexual organ of the plant); specifically in the mother part of the flower, in the embryo sac

describe a pinnately compound leaf, a bipinnately compound leaf, and a tripinnately compound leaf

leaflets are attached to a rachis, which is an extension of the petiolule (middle segment of "stem") *simple pinnately compound leaf*: there is a single rachis to which the leaflets are attached *bipinnately compound leaf*: first rachis or primary rachis branches into secondary rachises where the leaflets are attached *tripinnately compound leaf*: there are rachises of the first, second, and third order

describe a palmately compound leaf

leaflets radiate from the upper end or tip of the leaf stalk; attached to a central rachis

what is a leaf?

leaves are: -lateral outgrowths of a plant shoot -usually determinate (finite growth) -vascularized -initiated by the shoot apical meristem -usually photosynthetic ---capture light and make sugars ---BUT some are not photosynthetic

BE ABLE TO LABEL THE CROSS SECTION OF LEAF

lec 4 slide 29

KNOW EVERYTHING ON "DICOT EMBRYO DEVELOPMENT" SLIDE

lecture 3 slide 13 and 15

BE ABLE TO LABEL IMAGE OF ROOT APICAL MERISTEM

lecture 3 slide 28

KNOW THE VARIOUS ROUTES OF CELL DIFFERENTIATION

lecture 3 slide 31

describe the cytoskeleton in plants

maintain integrity of their cells *composed of*: -microfilaments -microtubules -intermediate filaments *functions*: -cell structure -movement -cell division (produces spindle, etc) -allows for transport (like interstate system)

what is leaf polarity

most dicots leaves have polarity--they are functionally different on their upper and lower surfaces *adaxial surface*: light harvesting (top) *abaxial surface*: transpirational water loss, respiratory gas exchange (bottom)

describe dicot leaf anatomy

most photosynthesis happens in the *palisade parenchyma* located directly under the upper epidermis -packed with chloroplasts -"mesophyll" also correct the bottom of the leaf (lower epidermis) contains guard cells and stoma -moist air sits between chambers on the bottom of the leaf; it enters and exits through the stoma (controlled by guard cells) -pathogens gain access through the stoma as well...upper epidermis is protected by the waxy cuticle KNOW DIAGRAM ON SLIDE 24 lec 4

plants, like most animals, are _________

multicellular eukaryotes

REVIEW SLIDE 8 OF LECTURE 3

need to be able to explain why each is important

at what stage of dicot embryonic development do we get the first notion of two cotyledons? two distinct cotyledons?

notion: heart stage distinct: torpedo

what do plant scientists often use to observe plant chromosomes in different phases of mitosis?

onion root tip: a rapidly growing part of the onion and thus many cells will be in different stages of mitosis

describe the middle surface of the leaf

parenchyma made of mesophyll tissue (*chlorenchyma*, a special type of ground tissue), which is composed of 2 types of cells: -*palisade cells*, which are specialized to perform most of the photosynthesis in the leaf -*spongy parenchyma cells*, which form a loose network of open spaces (like a sponge), where gases for photosynthesis can be contained (CO2, H2O, O2) xylem and phloem cells are arranged in bundles that form veins to help the palisade cells conduct photosynthesis and cell respiration -xylem delivers water for photosynthesis -phloem picks up sugars that have been produced in the palisade cells to transport to the rest of the plant (in the form of sap)

what is phyllotaxy? explain

phyllotaxy is the pattern of organ initiation at the shoot apical meristem can be: -*alternate* (grasses) ---one leaf at a time -*opposite* (most common) ---two leaves at a time, 180 degrees apart at each node; sometimes pairs alternate by 90 degrees at successive nodes -*whorled* ---three or more leaves at each node; small spacial dift with each node -*spiral* ---leaves form at about 137.5 degrees apart creating a spiral pattern ---the angle of leaf placement dissects the apex by the golden ratio of 1.618 !!!

how does plant cell division (mitosis) differ from animal cell division?

plant cells DON'T have centrioles REVIEW SLIDE BEFORE EXAM

in what ways do plants provide us with more than food?

plants: -are sources of novel therapeutic drugs -provide better fibers for paper or fabric ---cotton is being bred for increased pest resistance and better fiber production -are sources of biorenewable products (biofuels) ---biodiesel produced from rape, algae, and soybeans are replacing petroleum-derived diesel ---sugars, starches, and cellulose can be fermented into ethanol ------corn was originally used but people were upset by this when countries are starving ------_Miscanthus giganteus_ is a fast growing perennial bioenergy crop that grows on land unsuitable for food production -provide renewable energy sources

plant embroys are _________

polar structures -one end is different from another the first sign of polarity in the zygote occurs within minutes of fertilization as a patch of F-actin accumulates at the site of sperm entry -have it BEFORE first division disorganization after fertilization--> polar nuclear migration (for F-actin route) or directional elongation (for MT)-->asymmetrical cell division

the embryonic root is also called the ______; explain

radicle *hypocotyl* = base of radicle *epicotyl* = base of plumule slide 3 lec 5/6

REVIEW SLIDE 34 IN LEC 3

secondary cell walls contain: -cellulose -hemicellulose -lignin -glycoproteins presence of hydrophobic lignin renders the secondary cell wall water proof for efficient water transport

further explain sieve cells (gymnosperms) and sieve-tube elements (angiosperms)

sieve cells (gymnosperms) are the smaller of the two -no nucleus at maturity but cytoplasm present -has albuminous cells that contain nucleus, deliver proteins and ATP to sieve cells; *derived from different mother cell than sieve cells* sieve-tube elements (angiosperms) appear larger because they have companion cells -sieve plates are located between two sieve-tube elements and they filter the phloem sap -the companion cell contains the nucleus, mitochondria, etc. ---super active; make mRNA and send them to the other cells ---sieve-tube elements do NOT have nucleus ------still alive though because they have cytoplasm, etc ------nucleus, mitochondria, etc destroyed from these because waste of energy; have companion cell to send over the mRNA ---sieve-tube elements = information highway!! all focus goes towards this ---companion cells are *derived from the same mother cell as sieve-tube elements* gymnosperms and angiosperms develop differently but have the same function! just not derived from the same mother cell WATCH VASCULAR TISSUE VIDEO ON CANVAS

provide some similarities and differences between the SAM and RAM

similarities: -group of undifferentiated cells actively dividing towards apex -next zone they elongate -then they differentiate differences: -RAM is NOT located at the very tip ---sits many layers (of cells) deep protected by root cap from animals, etc.

describe the cell wall in plants

structure -*primary wall*: EVERY plant cell has a primary wall; surround growing cells -*secondary walls*: only present in plant cells that are specialized ---thickened structures ---containing lignin ---surround specialized cells e.g. vessel elements or fiber cells ---presence of a very thick secondary wall will result in death of the cell--maintained as a structural element application to human life -*dietary fiber*: healthy digestive system; high fiber diet = lots of plant cell walls -*biofuel*: bioethanol is accomplished by fermentation of polysaccharides in the plant cell wall

what are some other functions of leaves?

support -ex of false trunk (supporting leaf bases that grow close together) and hooks (spikes on the trunk that catch things) absorption -ex of thin, uncutinized epidermis (gas exchange under water) and insectivorous leaves attraction -ex of petalloid bracts or bright coloration of entire blade or portion of blade reproduction -plantlet develops at certain parts along the leaf of Kalanchoe (vegetative reproduction) protection -ex of bud scales or leaves reduced to spines storage -ex of fleshy or thickened blades (aloe), bulbs (vacuole), or pocket leaves

describe differentiation of cells in the epidermis

the leaf epidermis comprises *pavement cells*, *trichomes*, and *guard cells* trichomes: -trichomes are epidermal hairs -some trichomes protect plants by deterring insects and herbivores --- some are multiple segments with droplet on end; attract caterpillars because they thin it's food (actually chemical labeling for predatory wasps --- some are sticky and collapse on insect; contain enzymes so start digesting the insect while it's trapped --- some reflect light to reduce UV and heat absorption --- seed trichomes such as cotton fibers help in seed dispersal -trichomes can be unicellular or multicellular, branched or unbranched, glandular or non-glandular -in Arabidopsis, many trichome mutant have been identified --- some mutants underproduce trichomes (perfectly smooth--removing trichome production gene) --- some mutants overproduce trichomes (removing trichome repressor gene)

describe the chloroplasts; what is their title

the leaf's key organelle -located in palisade and spongy cells in the chlorenchyma mesophyll where photosynthesis takes place (more in palisade layer) -green cells contain *thylakoids* ---thylakoids = sacs that contain chlorophyll to trap light ---when thylakoids are stacked, they are called *granum* (plural are grana)

how are land plants diverse?

the simplest land plants have no vascular system, they get water through absorption; broad-leafed flowering plants have vascular systems and reproduce sexually

what is the most important job of the leaf? describe the upper surface of the leaf

to provide a large surface area for photosynthesis to take place upper surface: made of a layer of dermal tissue called the epidermis -*epidermal cells* secrete a waxy *cuticle* (top layer) that: ---helps reduce water evaporation off the leaf ---protects the leaf so it can perform its primary function, photosynthesis ---sunlight passes through epidermal cells to photosynthesizing cells in the palisade parenchyma

name the two-membrane organelles and the single-membrane organelles

two-membrane: -plastids (involves chloroplasts) -mitochondria single-membrane: -peroxisomes -vacuoles (vacuole membrane is called *tonoplast*)

how does the root endodermis act as a selectivity filter?

vascular bundle is surrounded by endodermis -everything outside of the vascular bundle = cortex -separated by the *casparian strip* ---HYDROPHOBIC! ---reinforcement that seals off the vascular bundle; water switches to active transports (symplastic pathway) ---water enters and passes through cell walls to the xylem; if toxic water, poisons the whole plant once in xylem ---casparian strip is *chemically different* from the rest of the cell wall; the cell wall contains lignin but not suberin whereas the casparian strip is made of suberin and sometimes lignin ------suberin is a waxy liquid (HYDROPHOBIC!) ------forces water to cross the plasma membrane (enters the root through apoplast--cell wall spaces-- until it reaches the casparian strip which blocks apoplastic water flow) root endodermis acts as a selectivity filter!! -primarily selects against sodium; plants DO NOT tolerate well

describe the vascular tissue system

xylem forms a plus sign shape in the ROOTS -if you see a plus sign--> root (test question) -transports water and provides physical support phloem fills in the corners of the plus sign -forms the vascular bundle together -transports water and nutrients like sugar throughout the plant -vascular commuication --> phloem!! *similarities*: both xylem and phloem can pump material from bottom to top (xylem: water and minerals; phloem: water and food) from bottom to top (root to shoot) *differences*: xylem only pumps water and minerals from bottom to top (unidirectional) while phloem can pump water and food bidirectionally (primary job is to pump from top to bottom tho); xylem is dead at maturity while phloem is living; phloem cells have end walls with perforations while xylem has no end walls between cells; xylem has thick walls stiffened with lignin vascular tissue also contains cambium so it has the ability to grow in thickness as the plant grows in thickness