BIO 201 Final Study Guide
BIO 201 Final Study Guide BIOL 201
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Date Created: 05/07/16
Exam 6 Study Guide Updated April 29, 2016 These are questions to guide your efforts to explore the material that we have discussed. Angiosperms II What are the general trends of trait evolution in terrestrial plants? Seeds enclosed in carpel that resembles a leaf that has folded over and fused at the margins; Pistil composed of a single carpel, or two or more united carpels; Seed develops from ovule within carpel; Ovary becomes a fruit. What are the general characteristics of the Magnoliophyta? What is shared with gymnosperms, what are the differences? Be able to pinpoint the fundamental differences in reproduction and life cycles! Divided into two large classes: Magnoliopsida – Dicots (Two cotyledons; DNA and cladistic evidence suggest two dicot groups, possibly more); Liliopsida – Monocots (Single cotyledon); Heterosporous; Sporophyte 2n generation dominant; Female gametophytes enclosed within sporophyte tissue and reduced to only a few cells; At maturity, male gametophytes consist of a germinated pollen grain with three nuclei; Both micro- (male) and megagametophytes (female) much reduced compared to non-flowering vascular plants What are the flower parts? How is the flower comprised of stem, nodes, internodes and whorls of leaves? What are the functions of flower components? Stamen: microspore producing organ: Anthers: fused, microspore-containing chambers; Filament: supports anthers Pistil: megaspore-producing organ: Stigma: area capturing the pollen; Style: elevates stigma to enhance pollination; Ovary: swollen base of the pistil, contains ovules; Ovule: More later Petals (corolla): odor + color to attract the pollinators, shape to make sure that the pollen sticks Sepals (calyx): protect the inner flower parts prior to opening Receptacle: tip of the flower stalk upon which the other parts are attached Peduncle: the main axis of an inflorescence on which individual flowers arise - stem What are the various ways flowers attract pollinators? shapes, colors, odors What is the importance of insect (or vertebrate) pollination and why is that an advantage over Gymnosperms? What defines the group we call the angiosperms? flowers How do the microgametophytes and megagametophytes develop in Angiosperms? What happens during pollination, how are the sperm delivered to the egg? In other words, details of Angiosperm lifecycle! How the female gametophyte is developed: Diploid megasporocyte differentiates in ovule. Undergoes meiosis and produces four haploid megaspores. Three degenerate. Remaining cell enlarges and nucleus divides to produce 8 nuclei (without walls). Outer two layers of ovule differentiate into integuments that later become seed coat. Micropyle at one end of ovule 8 nuclei form two groups, 4 near each end of cell. One nucleus from each group migrates to cell middle and forms central cell. Cell walls form around remaining six nuclei. Egg and two synergids closest to micropyle Three antipodals at opposite end - No apparent function Female gametophyte (megagametophyte, embryo sac) = large sac containing 8 nuclei and 7 cells How the male gametophyte is developed: Formation of male gametophytes in anthers. Four patches, corresponding to pollen sacs, of microsporocyte cells differentiate in anther. Each microsporocyte undergoes meiosis to produce quartet of haploid microspores. Microspores undergo three important changes: Divide once by mitosis to form a small generative cell inside the larger tube cell Nucleus of tube cell = vegetative nucleus Members of each quartet of microspores separate. Wall becomes two-layered. Outer layer = exine Finely sculptured Contains chemicals that may react with chemicals in stigma Generative nucleus will later divide to produce two sperm Compare the lifecycles of Gymnosperms and Angiosperms! What is difference between pollination and fertilization? Pollination - Transfer of pollen grains from anther to stigma (Self-pollination - Pollen grains germinate on stigma of same flower); Fertilization - Union of sperm and egg How do plants control against self-pollination and against pollination by non- conspecifics? What is the importance of endosperm to humans? Major source of human nutrition: wheat, rice and corn What is the advantage of pollination by insects (or other vectors) over wind pollination? Less pollen needs to be dispersed compared to wind pollination - lesser energy consumption ?) Angiosperms: all of the above: have seeds, flowers, endosperm, and double fertilization; E all of the above ?) What is the key difference between meiosis in flower ovary versus stamen? no A, B!, no C, no D; A Nothing, they are basically the same; B Only one female meiotic product survives; C Only one male meiotic product survives; D Meiosis only occurs in the ovary Embryogenesis: flowers to seed and fruit What are the differences between Dicotyledonous and Monocotyledonous plants? How do embryos develop in the Angiosperms? fertilization -> zygote lies underneath the endosperm -> endosperm divides to produce mass of endosperm tissue surrounding the embryo -> zygote divides to form 2 parts: embryo and suspensor -> suspensor anchors embryo and transfers nutrients -> embryo differentiates to cotyledons, epicotyl, hypocotyl, radicle, apical meristems -> endosperm = food for developing embryo and cotyledons; however, cotyledons are nutrition source for seedling -> monocots: cotyledon transfers food from endosperm to embryo How do flowers spread their pollen? What is the origin of the flower parts? Life cycle! How is Angiosperm life cycle different from the gymnosperm life cycle? *see previous section for this question What is the function of cotyledons in monocots, what in dicots? Monocots: transfers food from the endosperm to the embryo; dicots: source of nutrition for seedling What happens to the endosperm during the embryo development in dicotyledonous plants? Food for cotyledons and embryo in dicots What is a fruit? Matured ovary and its accessory parts (Contains seeds, all fruits develop from flower ovaries and accordingly are found exclusively in flowering plants) What is a fleshy fruit? How is this different from dry fruit? Mesocarp fleshy or dry at maturity; Exocarp – Skin; Endocarp - Inner boundary around seed(s); Mesocarp - Tissue between exocarp and endocarp How do the pomes develop? Flesh comes from enlarged floral tube or receptacle that grows up around ovary; Endocarp papery or leathery; Apples, pears - Core and a little of adjacent tissue is from ovary; remainder is from floral tube and receptacle What is the difference between dehiscent and indehiscent fruits? Dehiscent split at maturity; indehiscent don’t split How are follicles and legume fruit different? Follicle - Splits along one side (Larkspur, milkweed, peony); Legume - Splits along two sides (Legume family: peas, beans, lentils, peanuts) How are siliques and silicles different? Silique - More than three times longer than wide; Silicle - Less than three times longer than wide. However, both split along 2 sides How are achenes and nuts different? Achene - Base of seed attached to pericarp (Sunflower seed, buttercup, buckwheat); Nut - Similar to achene, but larger, with harder and thicker pericarp, and a cluster of bracts at base (Acorns, hazelnuts, hickory nuts) How are simple and aggregate fruits different? Simple fleshy fruits develop from flower with single carpel within a pistil; Aggregate Fruits: Derived from single flower with several to many pistils, individual pistils mature as clustered unit on single receptacle How are fruit/seeds dispersed by insects and vertebrates? Seeds pass through digestive tract; Fruits and seeds adhere to limbs, fur, or feathers; Oils attract insects (Elaiosomes on bleeding hearts used as food by ants) What is the difference between epigeous and hypogeous germination? Epigeous germination: Hypocotyl lengthens, bends and becomes hook- shaped; Top of hook emerges from ground, pulling cotyledons above ground; Hypogeous germination: Hypocotyl remains short and cotyledons do not emerge above surface What is needed for seed germination? Water, temperature, light, scarification How does the germination proceed in plants? Are there any differences between monocotyledonous and dicotyledonous plants? What do the cotyledons do during the germination? radicle emerges -> cotyledons emerge or stay underground (epigeous or hypogeous) -> in grasses, coleoptile and coleorhiza protect the emerging leaves/radicle How does the seed viability/dormancy vary – what are the extremes that we know? depending on species and storage conditions; Viability extended: At low temperatures, when kept dry What is William Beal’s experiment all about? How long a seed can stay dormant and still germinate and grow; 200 yrs old currently; supplemental reading that claims a frozen seed germinated from 30,000 yrs ago How long can a seed remain dormant, yet viable? See above question In which order did the character (trait) evolution among land plants occur? How about among seed plants? Hint: look into the phylogenetic trees and the characters mapped into them. Is there anything that makes flowering plants better adapted to terrestrial environment than other seed plants? ?) angiosperm microgametophyte has... pollen grain, A at most 3; A Three nuclei or cells; B Eight nuclei or cells; C 3n endosperm; D Central nuclei; E Most but not all of the above ?) Seed germination may be stimulates by... A acid, B grinding, C water; all of the above! ?) Both gymno- and angiosperms have… no A Ovaries; YES B Meiosis followed by nuclear divisions without cytokinesis; no C Fruit; no D A and B; no E A and C Plant structures Why do some bog plants benefit from a carnivorous habit? What are the different strategies of carnivorous plants for capturing insects? Drosera, Dionaea and Sarracenia insect trapping leaves What are the structural components of stems, roots, and leaves? Stem: Node = areas of leaf attachment; Internodes = space between the nodes Roots: Epidermis = thin; 1 cell layer; usually with trichomes; Vascular tissue = xylem and phloem; Cortex = tissue between epidermis and vascular tissue DI; Pith = central parenchymatous tissue specialized for storage DI What are the different functions of the stems, roots, and leaves; what are their modifications? Stem: support the photosynthetic organs; some stems are photosynthetic (Ephedra, Psilotum, Equisetum); storage for water/starch (cactus); transport water and stuff between roots and foliage (vascular tissues); Modifications: Stolons (strawberry); Tendrils (Virginia creeper); Cladophylls (butcher’s broom); Thorns (honey locust); Succulent stems of cacti Leaf: petiole (continues as midrib which branches into veins in the blade[megaphyll]); damaged/old leaves are released by abscission; Modifications: Tendrils of a sweet pea; Ocotillo and cactus spines; Window leaves of the elephant plant; Bracts of the Indian paintbrush or poinsettias (these are not true sepals or petals) Root: Anchorage; Storage - biennials (carrot, beet) store energy and carbon necessary for flowering in their roots; Absorption - water and minerals; Transport - transportation of water and minerals to the shoot; Modifications: Storage - beets, turnips, radish, cassava, sweet potato; Aeration – mangrove; Movement - contracting roots of lilies and ginseng What is leaf abscission; how does it work; what is its importance? Abscission: Abscission zone has less sclerenchyma and cells are thin-walled; Abscission auxin and ethylene controlled; Cells along the abscission layer suberize (separation layer); The purpose: isolate the leaf and protect the plant from infections and desiccation (Suberin = fatty substance in cork layers and in casparian strips) Where does photosynthesis occur and why? What is spongy mesophyll and why is it spongy? What is palisade mesophyll and what is the purpose of its structure? What is a root cap? How does it function? How does it grow? one meristem pushing cells forward; Cell differentiation to columella cells (Amyloplasts(= starch containing plastics(?))- gravitropism? plants still feel gravity(?)); Peripheral cells (Shed off - root cap turn over); What is mucigel? Why is it important? How about columella/peripheral cells? Mucigel: Slime comprised of polysaccharides; A root can produce mucigel up to 10% of its own weight daily; Several functions of mucigel: 1. Protection - layer of slime 2. Lubrication - with the shed peripheral cells 3. Water absorption – absorbent 4. Nutrient absorption - Mucigel increases root contact with soil water What/where is endodermis? What does it do and why? Endodermis (“Last line of defense” - casparian strip/ Suberized layer forcing the apoplastic flow into the intracellular space - symplastic flow) What is the purpose of casparian strip? See question from lecture below What/where is pericycle? What is its importance to lateral root development? What are the differences and similarities of the monocot and dicot stems, roots, and leaves? monocot <- root -> dicot monocot <- stem -> dicot ?) Carnivorous plants… A Live in environments high in N B Live in environments high in P YES C Live in environments low in N D Live in environments low in P ?) Tips of the roots may have… no A No meristems whatsoever no B Only one meristem YES C Two meristems D Up to three meristems ?) Casparian strip… no A Protects the vascular cylinder in shoots no B Is easily permeable to liquids YES C Forces liquids into the cells no D Allows intercellular flow of liquids and nutrients no E Contains apical meristems Plant growth and development What are primordia? Leaf primordia control procambial differentiation What is cambium, what is procambium? What are their functions? What do they produce? 1) Vascular cambium (Produces secondary xylem and phloem (bifacial cambium)); 2) Cork cambium – phellogen (Produces periderm and secondary cortex) What is protoderm? What does it produce? Epidermis of a shoot How do the apical meristems and axillary buds interact – hormonally and developmentally? What is apical dominance, what is its importance? apical meristem controls axillary buds hormonally - the axillary buds replace main shoot, if it gets damaged What are intercalary meristems, where are they, and what are they an adaptation to? Between mature tissues at the bases of the nodes and leaf sheaths; Allow growth in absence of apical meristem - important for adaptation to herbivory in grasslands; Grasses How do leaves grow? Leaf primordium below protoderm (forms epidermis); The primordium has an apical meristem and a procambial strand that forms the midrib; Meristem facing the shoot thickens the leaf; Leaf contains marginal meristems (note; not only apical) that form the blade and the petiole; Cellular expansion and division of the marginal meristems results in leaf growth How do roots grow? What are the different regions that we consider, what happens in each of those? Root cap: Own meristem pushing cells forward; Cell differentiation to columella cells Region of cell division: Small, densely cytoplasmic cells; Includes the apical meristem Region of cell elongation: Elongation by filling vacuoles with water Region of cell differentiation: Indicated by presence of root hairs (trichomes); Non-elongating region of the root; 95% of the plants belong to mycorrhizal families; mycorrhizal colonization results usually in loss of root hairs - see the pine root... What do trichomes do? Trichomes = root hairs. Increase surface area to obtain more nutrients What do root hairs do? See above What is primary/secondary growth? Primary: elongates; secondary: thickens What are the evolutionary advantages of secondary growth? Without circulatory and excretory systems, plants can build new tissues and discard wastes into the older tissue Primary tissues may not be enough to support tall plants - competitive advantage to plants that elevate their photosynthetic tissues higher What is vascular cambium, what does it produce? Secondary cambium; secondary xylem and phloem (bifacial cambium) How does procambium develop/differentiate to vascular cambia in roots and shoots? What is periderm, what are its components? Bark: 1) Phellogen - the second cambium (Cork cambium - originates from the cortex, secondary phloem, or epidermis; Secondary growth usually ruptures the periderm - necessary to keep adding new layers from the inside) 2) Phellem – cork (Outer derivative of the cork cambium; Dead and heavily suberized) 3) Phelloderm - secondary cortex (Inner derivative of the cork cambium; Cells alive, not suberized) What is phellogen and what does it produce? See above question Why is there summer and spring wood? How about heart- and sapwood? Spring (early) and summer (late) wood (Because of the environmental conditions and control by hormones (decline in auxin), summer wood is denser than spring wood) Sapwood conducts water and minerals (hydrogels +their function in xylem) Heartwood is a non-conductive landfill. Without circulatory/excretory systems, this is where many wastes - resins, tannins, gums and oils deposit What is bark? What are its components? Is old secondary phloem incorporated to this? All tissues outside the vascular cambium are bark; Two components: 1) Secondary phloem - phloem produced by vascular cambium; 2) Periderm - suberized layer that protects and insulates the inner tissues How do monocots go through secondary growth? How common is that? The outer derivative of the cambium is secondary cortex, the inner is procambial strands (future vascular bundles) and the conjunctive tissue (parenchymatous spacer tissue between the vascular bundles); Rarely present - exceptions: tree-like monocots Dracaena and Cordyline ?) Hollow trees can be alive because… no A The canopy is spatially separated from the roots no B The canopy functions as an independent photosynthetic entity no C The center of the stem can rejuvenate and maintain function YES D Only the outer parts of the trees are metabolically active and alive ?) There are ______ lateral cambia. no A One that produces vascular tissues no B Two that produce xylem and phloem YES C Two that produce cork and vascular tissues no D Three that produce xylem and phloem and cork no E Four that produce xylem, phloem, cork and secondary cortex Plant hormones What is a hormone? Production dictated by genes; Mostly produced in actively growing regions; Produced and active in smaller amounts than vitamins and enzymes Distinguish between growth, differentiation, and development. How are the three different conceptually? Growth: Irreversible increase in mass by division and enlargement of cells (divide and enlarge) Differentiation = Cells develop different forms adapted to specific functions Development = Coordination of growth and differentiation of a single cell into tissues and organs Distinguish between nutrients (CHNOPS), vitamins, and hormones. How are their purposes different for plants? Nutrients = Substances that furnish elements and energy to produce organic molecules (obtained from air and soil) Vitamins = Organic molecules of varied structure that participate in catalyzed reactions, mostly by functioning as electron acceptor or donor; Synthesized in cell membranes and cytoplasm; Required in small amounts for normal growth and development Hormones = Production dictated by genes; Mostly produced in actively growing regions; Produced and active in smaller amounts than vitamins and enzymes What are the components of hormone function? 1) chemical: stimulus or inhibition of plant function - alternatively, interaction with inorganic compounds and other plant hormones; 2) regulation of gene expression: Hormones activate the genes to be transcribed and expressed as proteins/enzymes Know the functions of auxin, gibberellin, cytokinins, ethylene and abscissic acid. Know the transport mechanisms of auxin, gibberellin, and ethylene. 1) Auxin - cell elongation and differentiation; transported through the parenchyma cells in cortex, pith or vascular tissue, polar 2) Gibberellin - cell division and flowering; transported (not polar like auxin) likely as solute - moves in all directions in xylem and phloem 3) Cytokinins - cell division and organ formation 4) Ethylene - fruit ripening, senescence; transported: large amounts produced in roots, shoot apical meristems, ripening fruit, and senescing flowers 5) Abscissic acid - stress hormone, e.g., stomatal closure [6) Brassinosteroids – development, growth, stress, etc.] What kind of experimentation lead to elucidation of phototropism, auxin, and auxin transport? When were these experiments conducted? What controls apical growth? What is apical dominance and how do we explain that? Apical meristem inhibits the growth and development of axillary buds; High auxin levels may stimulate ethylene (another hormone) production. Ethylene then puts a lid on axillary bud growth - a marvelous example of hormone interaction How do young leaves (or leaf primordia) and axillary buds interact with the apical meristem? See above question Auxin – how is it transported, how does it function, and what are its effects on plants life? Growth control is not a function of the tip, but rather something transported from the tip; Auxins transported through the parenchyma cells in cortex, pith or vascular tissue; Polar movement in both roots (towards the tip) and stems (towards the base); Polar movement: Possibly by carrier proteins in the cell membranes and consumes energy – ATP; Auxin is mainly involved in cell elongation, not cell division What is the acid growth hypothesis? Auxin stimulates acquisition of H+ into the cell (H+ pumps in the cell membrane pump H+ against the gradient into the cell); Lower pH (higher H+ concentration) activates enzymes that break bonds among the cellulose fibers. This results in increased plasticity; After breaking the bonds mere turgor pressure stretches the cell Acid growth hypothesis may only explain some (early stages) of the cell elongation How is auxin involved in apical dominance, leaf abscission, cambial function/differentiation, and tropisms? In addition to simple chemical control of the cell structure and function, auxin likely induces gene expression for protein(s) necessary for cell growth; Apical dominance: Apical meristem inhibits the growth and development of axillary buds; High auxin levels may stimulate ethylene (another hormone) production. Ethylene then puts a lid on axillary bud growth - a marvelous example of hormone interaction; Leaf abscission: Auxin inhibits senescence and abscission; Environmental stimuli in the fall decrease auxin production; This allows the abscission to begin; Vascular cambium - activation and differentiation: Activated in the spring by auxin from the apical meristems and young leaves; Sucrose concentration regulates differentiation to phloem and xylem What are the interactions between auxin and other hormones or organic and inorganic molecules? What led to the discovery and identification of gibberellin? Gibberellins – functions in plant and differences between gibberellin effects and auxin effects! cell division and flowering; Gibberella fujikuroi: Silly rice disease in Japan caused abnormal growth of rice; The causal agent was Gibberella fujikuroi, a root pathogen; Gibberella is better known by its conidial (asexual) state - Fusarium; In rice, the disease symptoms were also induced by fungal extract or the filtered culture media; Conclusion, Gibberella fujikuroi produced and secreted a water-soluble compound that controlled rice growth - gibberellin Not polar like auxin. Likely as solute - moves in all directions in xylem and phloem Growth stimulant: Internodal elongation in mature regions of plants; Cell elongation and division (auxin only in elongation). The mechanism does not involve cell wall acidification or H+ pumps What are gibberellin functions in seed germination? Imbibition releases gibberellin from the embryo; Gibberellins launch the transcription of the genes coding for hydrolytic enzymes - amylases; Amylases catalyze starch conversion to sugar; energy and stimulant for the growing embryo Cytokinin – effects and interactions with auxin? cell division and organ formation: Cell division: Accelerates cell cycle - effect depends on auxin concentration; Stimulation of cell expansion and division in cotyledons: Does not involve wall acidification like proposed for auxin; Tissue differentiation and organ formation: The ratio of auxin/cytokinin determines which organs produced; Like auxin, inhibits senescence How does hormonal manipulation assist in explant propagation? Ethylene – effects, interactions with auxin; leaf abscission in particular! fruit ripening, senescence; This is our first gaseous plant hormone; Known since Egyptian times; Large amounts produced in roots, shoot apical meristems, ripening fruit, and senescing flowers How is ethylene involved in fruit ripening – what does it specifically do? Several components in the process: Pigment degradation; Enzymatic cell wall degradation; Enzymatic conversion of starch to sugars How do we use ethylene for commercialization of farm products (Hint: flavr savr)? Commercial tomatoes are typically “flavr savr” tomatoes; Mutated pectin/cell wall breakdown gene; Prevents ripening in absence of ethylene; Garden or farmers market tomatoes typically are not ripened this way Abscissic acid – effects, stomatal closure in particular! stress hormone, e.g., stomatal closure abscissic acid has nothing to do with the leaf abscission; Known as the stress hormone. Counteracts the stimulatory effects of auxin, gibberellins, and cytokinins; One extremely important function - stomatal closure How do the stomata work? Recall the O1-O4 and C1-C4… Brassinosteroids – what are they and what do they do? development, growth, stress, etc.; Brassinosteroids (BRs) are a family of > 50 structurally related compounds that contribute to: Growth; Cell division, elongation, and differentiation; Defense against pathogens; Stress tolerance; Reproductive development; BL is not very abundant in plant tissues; Brassinolide and castasterone are steroids like some animal hormones How can we use mutants to elucidate gene functions? Think knock-outs, wild types, and restoring a phenotype! ?) Plant hormones can be produced… yes (transport) A in one part of a plant and have an effect in another yes B by one plant and have an effect in another plant yes C by one plant species and have an effect on another yes D by a non-plant and have an effect on a plant therefore this is the correct answer E All of the above ?) Growth stimulated by IAA involves… no A Accelerated cell divisions no B Breaking of the cell wall or its chemical structure seems legit C Filling of the vacuoles D A and C THIS ONE! E B and C ?) Which of the following is most true? no A One hormone; one function maybe, maybe not B One hormone; chemical control of function YES C One hormone; hormonal control of function Plant tropisms What is a tropism? What controls these tropisms? in general the plant responses to various external stimuli What environmental stimuli do plants respond to? This is that long list of tropisms that we talked out… hydro-, chemo-, thermo-, traumo-, electro-, and aerotropism Four kinds we talked about: Phototropism; Gravitropism; Thigmotropism; Heliotropism How does phototropism work? Light causes auxin (IAA) to accumulate on the shaded side of the stem; Result, increased rate of cell elongation on the shaded side - curvature towards light How does the gravitropism work? What is the hypothesis for amyloplast function in gravitropism? Is there an alternative that might work equally well for both roots and shoots? What is it? Amyloplast deposition - old school idea about gravitropisms; We know better now… lack amyloplasts and the root still goes towards the center of the earth because of hormones A fine example of hormone-inorganic compound interaction: Ca2+ accumulation triggers IAA accumulation which in roots inhibits elongation; Similar mechanism possibly involved in shoots: IAA accumulates in the lower side of the horizontally oriented stem Who uses thigmotropism? How does it work? Plant response to contact with solid objects; Examples include tendrils of peas and many climbing vines; This coiling is similar to the phototropism – i.e. the coiling occurs as a result of the unequal elongation of the cells – the cells opposite to the stimulus expand faster; Sometimes turgor movements, which are not thigmotropisms per se, are included under this category of responses What is the difference between thigmotropisms and turgor movements? Turgor movements: include barberry anther responses to pollinators and the bush monkey flower stigma folding to retain pollen. *see previous question for thigmotropisms What are our examples for turgor movements? What is their evolutionary significance? A curious and cool example is also the sensitive plant (Mimosa pudica) response to touch; The response is a K+ ion migration induced rapid movement of water; K+ ions rush from one side to another changing the osmotic potential – water follows and loss of turgor on the flaccid side folds the leaf and leaflets; Similarly to the sensitive plant, the venus flytrap closure is a result of sudden expansion of the outer epidermal cells; Cells in an outer epidermis are compressed. This creates tension in the plant tissue that holds the trap open; Mechanical stimulus of the trigger hairs initiates ATP-driven water pressure changes; The cells expand by the increasing water pressure, and the trap closes as the tension relaxes How do the turgor movements work in the Venus flytrap and in the sensitive plant? Similarly to the sensitive plant, the venus flytrap closure is a result of sudden expansion of the outer epidermal cells; Cells in an outer epidermis are compressed. This creates tension in the plant tissue that holds the trap open; Mechanical stimulus of the trigger hairs initiates ATP-driven water pressure changes; The cells expand by the increasing water pressure, and the trap closes as the tension relaxes What is photoperiodism? Controls flowering, senescence, and dormancy (plants change colors cause saving resources for winter); Shortening days launch a chain reaction that results in non-replacement of chlorophyll, making the yellow and red pigments (carotenoids and anthocyanins) visible; Shortening of days results ultimately in dormancy - period of decreased metabolism How are plants categorized based on their photo-dependency? What does it mean to be a short day or a long day plant? Neutral - day length has no effect; Short-day - flower when days shorter than critical length; Long-day - flower when days longer than critical length; Intermediates How do plants measure the day length? (Hint: study the Pr – Pfr conversions.) ?) Phototropism is a result of… YES A Faster growth rate on the shade side of the plant no B Faster growth rate on the sunny side of the plant YES C A result of a hormone’s sensitivity to light A and C (growth elongation on the shade side) B and C ?) Plant responses to external stimuli... yeah A Facilitate pollination yeah B May be selected for because they are advantageous probs not C Lack evolutionary significance YES D A and B E None of the above Environmental change What is the present human population? What are the predictions for human population dynamics and why? >7 billion today; 2030 >9 billion What do the human population dynamics mean to resource use and resultant environmental changes? Why? What is land transformation? What are its effects to organismal diversity, to biogeochemical cycles? Clearing land for agriculture, Deforestation because of silviculture and failure to reforest; 10-15% of all Earth’s land surface is occupied by row crops or industrial areas industrial areas and crop lands are biological deserts in terms of biodiversity; 6-8% of all Earth’s land surface is pasture - these neither include native grasslands (pampas, Australia, American prairies) that are used for grazing, nor forested areas in active or intensive silviculture; Land transformation also impacts climate: 20% of the anthropogenic CO2 emissions result from land transformation; The burning of organic materials contributes by release of greenhouse gases and pollutants: CH4 and NOx (CH4 is more potent greenhouse gas than CO2, NOx contributes to acid rain); Human alteration of the biogeochemical cycles: Humans have a substantial impact on the carbon, hydrological, and nitrogen cycles What is the proportion of the landmass that is covered by human activities? 10-15% What are the human impacts in the marine ecosystems? Why are the marine systems disproportionately affected? 50% of the coastal mangrove forests have been cleared by human activity, Commercial fishing is predicted to collapse by 2050; Humans use only c. 8% of the NPP of the marine ecosystems, but 25-35% in the temperate up swelling and shelf areas What are the human impacts on global C cycle? What are the drivers of these impacts? What is the magnitude of human impacts? What are the outcomes of these impacts? C6H12O6+6O2<=>CO2+6H2O; Four major pools: Ocean, Soils, Atmosphere, Vegetation; Plants take up CO2; All organisms respire; Large quantities diffuse in and out of the oceans; Combustion: Mainly fossil fuels, stowed away during the carboniferous (286- 360mya) or prior; Increase in the atmospheric CO2 concentration; Land transformation: Decreasing size of the vegetative C pool; Decreasing photosynthesizing pool; Effects of increasing CO2 concentration on vegetation: CO2 fertilization - likely improves plant growth; Decreased food quality for herbivores - C/N ratios; Slower rate of decomposition - C/N ratio; Four major pools: Ocean, Ice and icecaps, Groundwater, Atmosphere; Evaporation and transpiration supply the atmospheric pool; Precipitation returns H20 to the other pools; Fresh water constitutes about 3% of the total supply; Globally, about 50% of the total fresh water supply is used by humans; 70% of this fresh water is used for agriculture; Examples of our water use: In US only 2% of the rivers run unimpeded; Colorado, The Nile and Ganges rivers are almost completely used prior to their reaching the ocean; Aral-sea was substantially reduced by irrigation: Decimation of endemic and native flora and fauna, Altered local climate, Exposed and airborne salt-rich sediments cause respiratory problems, miscarriages and increase cancer; In arid regions within US, groundwater mining exceeds recharge endangering sustainable supply of fresh water What is the magnitude of the human impacts on global water cycle, especially on the fresh water supply? What are the drivers of these impacts? What is ground water mining? Is it sustainable? *see above question What is the magnitude of the human impacts on global N cycle, especially on the fresh water supply? What are the drivers of these impacts? What are their consequences? Atmosphere is 78% N2 - not available to plants; How do plants get their N: Atmospheric N is fixed by bacteria and then maintained in the biotic pool through decomposition; Atmospheric N is fixed by humans and incorporated into the terrestrial and aquatic pools (dead zones) and volatilized into the atmosphere; Let’s look at the totals: Global bacterial fixation c. 170 million tons; Human input as fertilizer 90-130 million tons; Cultivation of crops with symbiotic N fixation (alfa-alfa) may add another 40 million tons; Combustion of fossil fuels will contribute c. 20 million tons; Land transformation may release another 50 million tons - WHY?; Consequences of the N cycle alteration: Added N increases productivity in the “non-target” ecosystems resulting in greater CO2 storage; Unfortunately, only some species are very responsive to N fertilization - potential loss of local biodiversity; The added N may leaching - N enters the ground water and in aquatic environments. This Eutrophication can increase algal blooms and oxygen demand in water ?) The main anthropogenic mechanism that drives human alteration of global systems is… A) private automobiles, B) fossil fuel mining, C) land transformation, D) human population size ?) Human effects on C cycle include: A) CO2 emissions B) modifications of C sequestration C) desertification D) ocean acidification E) all of the above ?) CO2 enrichment A) makes plants grow faster B) makes animals grow slower C) bleaches coral reefs YES D) all of the above E) none of the above ?) Ground water mining means A) insertion of mines in the water table B) removal of historic water reserves for current use C) using wells for irrigation D) A and B YES E) B and C ?) Human population A) is small enough not to have global consequences B) is consuming less resources than are sustainably available C) is the likely cause of the on-going mass extinction YES D) all of the above Exam 6 Glossary. Updated April 29, 2016 Abscissic acid (ABA): growth-inhibiting hormone of plants; involved with other hormones in dormancy Abscission (leaf): separation of leaves, flower, fruits from plant after formation of abscission zone at the base of petioles, peduncles, pedicels Achene: single-seeded fruit in which the seed is attached to pericarp base Aggregate fruit: fruit derived from single flower with many pistils Alternation of generations: alternation between haploid gametophyte and diploid sporophyte in the life cycle of sexually reproducing organisms Amyloplast: colorless, starch-forming plastid found in roots and involved in gravity perception Angiosperm: plant whose seeds develop in ovaries that mature to fruits Annual: plant that completes entire life cycle in a year or single growing season Anther: pollen-bearing part of stamen Antipodals (of the embryo sac): relating to or denoting cells formed at the chalazal end of the embryo sac Apical dominance: suppression of growth of lateral buds by hormones Apical meristem: meristem at the tip of a root or shoot Archegonium: multicellular female gametangium of bryophytes and most vascular plants (other than angiosperms) Auxin: growth-regulating substance produced naturally or synthetically by plants Axillary buds: a bud that grows from the axil of a leaf and may develop into a branch or flower cluster Berry (True Berry): thin-skinned fruit that develops from compound ovary and normally contains more than one seed Biennial: plant that normally requires 2 seasons to complete its life cycle (first season is strictly vegetative) Bifacial cambium: seen in angiosperms; both xylem and phloem have secondary growth; secondary xylem=wood, secondary phloem= bark Bisporangiate strobilus: flower; structures include: receptacle, ovule, petal, sepal, carpel=pistil, (stigma, style, ovary), stamen (anther, filament) Blade (leaf): flattened part of leaf or seaweed Bract: usually leaf-like and modified in size, shape or color Brassinosteroid: (BRs) are a class of polyhydroxysteroids that have been recognized as a sixth class of plant hormones. These were first explored nearly 40 years ago, when Mitchell et al. reported promotion in stem elongation and cell division by the treatment of organic extracts of rapeseed (Brassica napus) pollen Calyx: collective term for sepals of flower Cambium: meristem producing secondary tissues Carnivory: plants that derive some or most of their nutrients (but not energy) from trapping and consuming animals or protozoans, typically insects and other arthropods Carpel: ovule-bearing unit that is part of the pistil Caryopsis: dry fruit in which the pericarp is tightly fused to the seed; indehiscent (doesn’t split) Casparian strip: band of Suberin around the radial and transverse walls of an endodermal cell Central cell nuclei (of the embryo sac): nuclei; frequently in 2s that unite with the sperm in embryo sac, forming a primary endosperm nucleus Cladophyll: flattened stem that resembles a leaf Coleoptile: protective sheath surrounding the emerging shoot of seedlings Coleorhiza: protective sheath surrounding the emerging radicle (immature root) Columella cell (root cap): Root cap cells differentiate first into columella cells Corm: vertically oriented, thickened food storage stem that’s enveloped by papery, nonfunctional leaves Corolla: collective terms for petals of a flower Cortex: primary tissue composed mainly of parenchyma; tissue usually extends between epidermis and vascular tissue Cotyledon: embryo leaf that usually either stores or absorbs food Critical day length: photoperiod Cuticle: waxy or fatty layer of varying thickness on outer layer of epidermis cells Cycadeoid: Bennettitales is an extinct order of seed plants that first appeared in the Triassic period and became extinct in most areas toward the end of the Cretaceous, although some Bennettitales appear to have survived into Oligocene times in Tasmania and eastern Australia. Some were characterized by thick trunks and pinnately compound leaves that bore a superficial resemblance to those of cycads, differing primarily in stomatal arrangement. The taxon comprises two groups, the Cycadeoidaceae, represented by Cycadeoidea and Monanthesia which had stout trunks and bisporangiate strobili, and the Williamsoniaceae including Williamsonia, Williamsoniella, Wielandella and Ischnophyton which had slender, branching trunks and either bisporangiate or monosporangiate strobili. Bennettitales have been placed among the anthophytes and for some time were considered to be close relatives of the flowering plants on account of their flower-like reproductive structures Cycadophyta: a division of extinct gymnosperms comprising the cycadophytes Cytokinesis: division of cell, usually following mitosis Cytokinin: growth hormone involved in cell division and other metabolic activities of cells Deciduous: shedding leaves annually Dehiscent: splitting at maturity along a built-in line of weakness in a plant structure in order to release its contents Dicotyledon: class of angiosperms whose seeds commonly have 2 cotyledons; “dicot” Dioecious: unisexual flowers or cones; male and female parts are on separate plants Diploid: 2 sets of chromosomes in each cell; characteristic of sporophyte generation Dormancy: period of growth inactivity in seeds, buds, bulbs, etc. when growth conditions are not ideal Double fertilization: event in angiosperms where 1 sperm fertilizes the egg (zygote) and the other sperm fertilizes the central cell (endosperm) Drupe: simple, fleshy fruit whose single seed in enclosed in hard endocarp Egg apparatus: located at the end of the embryo sac closer to the micropyle (the opening through which pollen nuclei enter the ovule.) Embryo: immature sporophyte that develops from a zygote within archegonium after fertilization Embryonic leaf: Upon germination, the cotyledon may become the embryonic first leaves of a seedling Embryophyta: the most familiar subkingdom of green plants that form vegetation on earth. Living embryophytes include hornworts, liverworts, mosses, ferns, lycophytes, gymnosperms and flowering plants, and emerged from Charophyte green algae Endocarp: innermost layer of fruit wall Endodermis: single layer of cells surrounding the vascular tissue in roots and some stems; cells have Casparian Strips Endosperm: food-storage tissue that develops through divisions of the primary endosperm nucleus; digested by the sporophyte after germination or before maturation Epicotyl: part of an embryo above attachment of cotyledons Epidermis: exterior tissue; usually 1 cell thick Ethylene: simple. naturally produced gaseous hormone that inhibits plant growth and ripens fruit Evergreen: a plant that retains green leaves throughout the year Exine: outer layer of the wall of a pollen grain or spore Exocarp: outermost layer of a fruit wall Extinction: they gone Fertilization: formation of a zygote through the fusion of 2 gametes Filament (of the stamen): threadlike body of certain bacteria, algae, and fungi; stalk portion of stamen Flower: plant structure containing reproductive organs and associated tissues Flower mimicry: poinsettia; where leaves look like petals of the flower Follicle: dry fruit that splits on one side Fruit: mature ovary containing seeds; reproductive structures of plants other than angiosperms Gametophyte: haploid, gamete producing Generative cell: cell of male gametophyte of angiosperms that divides into 2 sperms (sterile and spermatogenous) Genotype: genetic constitution of an organism; may or may not be seen Gibberella fujikuroi: A fungal pathogen that causes bakanae disease, a seed- borne disease of rice that is characterized by the growth of excessively long internodes, through its production of plant growth hormones called gibberellins Gibberellin: plant hormone that has a variety of effects on growth; known for elongation Gnetophyta: gymnosperm plants with some features similar to those of angiosperms, such as xylem with vessels, strobili resembling inflorescences, and the absence of archegonia. The genus Ephedra, well-known as a source of stimulant compounds, is classified among the gnetophytes Grain: see caryopsis Gravitropism: growth response to gravity Ground tissue: The tissue of a plant other than the epidermis, periderm, and vascular tissues, consisting primarily of collenchyma, parenchyma, and sclerenchyma. Cortex and pith are types of ground tissue Ground water mining: removal, or withdraw, of water in the natural ground over a period of time that exceeds the recharge rate of the supply aquifer. It is also called "overdraft" or "mining the aquifer." Ground water is contained in specific rock units called aquifers Guard cell: 1 of a pair of specialized cells surrounding stomata Gymnosperm: plan whose seeds are not enclosed within an ovary during their development Haploid: 1 set of chromosomes per cell; gametophyte Heartwood: nonliving, darker-colored wood whose cells have ceased functionality in water conduction Heliotropism: the directional growth of a plant in response to sunlight Herbivory: the eating of plants, especially ones that are still living. "in response to herbivory, plants defend themselves with arrays of structural and chemical weapons" Hesperidium: a fruit with sectioned pulp inside a separable rind, e.g., an orange or grapefruit Heterosporous: producing two different kinds of spores. Heterospory: production of both micro and megaspores Homospory: the production by various plants (as the club mosses and horsetails) of asexual spores of only one kind Hormone: organic substance produced in minute amounts in one part of the organism then transported to another part where it controls growth and development Hypocotyl: portion of an embryo/seedling between radicle and cotyledons IAA: a plant hormone promoting elongation of stems and roots Imbibition: absorption of water and swelling of organic materials because of the adhesion of the water molecules to internal surfaces Indehiscent: (of a pod or fruit) not splitting open to release the seeds when ripe Integument: outermost layer of an ovule; usually develops into seed coat; gymnosperm ovule has single integument, angiosperm usually has 2 Internode: stem region between nodes Intine: the inner mostly cellulose wall of some spores and especially pollen grains Knock-out (gene): genetic technique in which one of an organism's genes is made inoperative ("knocked out" of the organism) Land transformation: Leaf Blade: the flat expanded part of a leaf as distinguished from the petiole Leaf Gap: parenchyma-filled interruption in a stem’s cylinder of vascular tissue right above where the leaf is attached to the stem Leaf Midrib: central vein of a pinnately veined leaf Leaf veins: Veins provide support for the leaf and transport both water and minerals (via xylem) and food energy (via phloem) through the leaf and on to the rest of the plant Legume: dry fruit that splits along 2 seams; seeds attached to the edges Lignin: polymer with which certain cell walls become impregnated Liliopsida: Long day plant: plant in which flowering is not initiated unless exposure to more than critical day length occurs Magnoliophyta: comprising flowering plants that produce seeds enclosed in an ovary; in some systems considered a class (Angiospermae) and in others a division (Magnoliophyta or Anthophyta) Magnoliopsida: valid botanical name for a class of flowering plants. By definition the class will include the family Magnoliaceae Megagametophyte: female gametophyte in angiosperms (70% of species contain 8 nuclei) Megaphyll: leaf with branching veins Megasporangium: sporangium where megaspores are formed Megaspore: spore that develops into female gametophyte Megasporocyte: diploid cell that produces megaspores upon undergoing meiosis Megasporophyll: small leaf that produces megaspores following meiosis Meiosis: 2 successive nuclear divisions through which segregation of genes occurs and the result is 4 haploid cells Meristem: region of undifferentiated cells where new cells arise Mesocarp: middle region of fruit wall that is between exo and endocarp Microgametophyte: the male gametophyte produced by a microspore Microphyll: leaf with single unbranched vein (no leaf gap) Micropyle: pore/opening in the integuments of an ovule through which a pollen tube gets to embryo sac Microsporangium: sporangium in which microspores are formed Microspore: spore that develops into a microgametophyte Microsporocyte: diploid cell that produces microspores after meiosis Microsporophyll: small leaf that produces microspores Midrib (leaf): central vein of leaf Mitosis: nuclear division (cytokinesis); chromatids separate and produce 2 identical daughter cells Monocotyledon: class of angiosperms whose seeds have single cotyledon; “monocot” Monoecious: unisexual male and female flowers/cones on the same plant Monophyletic: (of a group of organisms) descended from a common evolutionary ancestor or ancestral group, especially one not shared with any other group Monosporangiate: Mucigel: slimy substance that covers the root cap of the roots of plants. It is a highly hydrated polysaccharide, most likely a pectin, which is secreted from the outermost (epidermal) cells of the rootcap Multinucleate: having multiple nuclei Mutant: (mutate): heritable change in DNA sequence Mycorrhiza: symbiotic association between fungi and plant roots Nitrogen fixation: the chemical processes by which atmospheric nitrogen is assimilated into organic compounds, especially by certain microorganisms as part of the nitrogen cycle Node (of stem): region where >1 leaves are attached Nut: one-seeded; dry fruit with hard/thick pericarp; develops with a cup or cluster at base Nutrient: substance that furnishes the elements and energy for the organic molecules that are building blocks Ovary: enlarged basal portion of pistil that contains ovules and develops into fruit Ovule: structure of seed plants that contains female gametophyte and potentially develops into seed Palisade mesophyll: mesophyll having 1 or more uniform rows of tightly packed columnar parenchyma cells beneath epidermis Parenchyma: thin-walled cells varying in size and function; most common type of cell Peduncle (of flower): stalk of a solitary flower or main stalk of inflorescence Pepo: any fleshy, watery fruit of the melon or cucumber type, with numerous seeds and a firm rind Perennial: plant that lives continuously after flowering Pericarp: collective term for layers of fruit wall Pericycle: tissue between endodermis and phloem of root; origin of lateral roots; 1-2 cells wide Periderm (stem): outer bark; mostly cork cells Peripheral cells: Petal: unit of corolla, usually flat and colored Petiole: stalk of leaf Pfr: form of phytochrome Phellem: a layer of usually suberized cells produced outwardly by a phellogen Phellogen: cork cambium Phenotype: physical appearance of an organism Phloem: food-conducting tissue of vascular plant Photosynthate: a sugar or other substance made by photosynthesis Phototropism: the orientation of a plant or other organism in response to light, either toward the source of light ( positive phototropism ) or away from it ( negative phototropism ) Phytochrome: protein pigment associated with absorbtion of light; found in cytoplasm of green plants and occurs in active and inactive forms; facilitates plants ability to detect light Pinophyta: also known as division Coniferophyta or Coniferae, are one of 12 extant division-level taxa within the Kingdom Plantae (Viridiplantae) and 10 within the extant land plants. Pinophytes are gymnosperms, cone-bearing seed plants with vascular tissue Pistil: female reproductive structure consisting of ovary, style and stigma Pith: central tissue of a dicot stem and roots; consists of parenchyma cells that become proportionally smaller as cambial activity increases the organs girth Pneumatophore: spongy root extending above the surface of the water; produced by a plant growing in water; facilitate oxygen absorption Pollen: (pollen grain): structure derived from the microspore of seed plants that develop into the male gametophyte Pollen tube: tube that develops from pollen grain to female gametophyte, delivering sperm Pollination: transfer of pollen from anther to stigma Pollination chamber: Polyphyletic: (of a group of organisms) derived from more than one common evolutionary ancestor or ancestral group and therefore not suitable for placing in the same taxon Pome: simple fleshy fruit whose flesh is derived from the receptacle Pr: form of phytochrome Primary phloem: Primary xylem: Procambium: primary meristematic tissue that differentiates into primary xylem and phloem Protoderm: primary meristem that gives rise to epidermis Protostele: a stele forming a solid rod with the phloem surrounding the xylem Pulvinus: an enlarged section at the base of a leaf stalk in some plants that is subject to changes of turgor, leading to movements of the leaf or leaflet Radicle: part of the embryo in a seed that develops into a root Receptacle (of flower): commonly expanded tip of a peduncle to which various parts are attached Rhizome: underground stem, usually horizontal; may look like a root but definitely has nodes and internodes Root: plant organ that functions in anchorage and absorption Root cap: thimble shaped mass of cells at end of root; functions as protection Root hair: delicate protuberance that’s part of the epidermis Samara: dry fruit whose pericarp extends around fruit to form a wing Sapwood: outer layer of wood that transports water and minerals; lighter in color Scarification: Schizocarp: twin fruit unique to parsley family Sclerenchyma: tissue composed of lignified cells with thick walls; functions in strength/support Secondary phloem: Secondary xylem: Seed: mature ovule containing an embryo and bound by a seed coat Seed coat: outer boundary layer of a seed; developed from integuments Seed dormancy: Sepal: unit of calyx that looks like reduced leaf; function in protecting unopen flower bud Short day plant: plant in which flowering is initiated when the days are shorter than its critical photoperiod Sieve element: Sieve plate: area of a wall of a sieve tube member that contains perforations that permit cytoplasmic connection between adjacent cells; the cytoplasmic strands being larger than plasmodesmata Sieve tube members: single cell of sieve tube Silicles: Siliques: dry fruit that splits along 2 seams with the seed on a central partition Siphonostele: Spine (of a plant): relatively strong, sharp-pointed woody structure on a stem; modified leaf Spongy mesophyll: mesophyll with loose cells arranged with air spaces; generally confined to lower part of interior of a leaf just above lower epidermis Sporangium: where spores are produced; uni or multicellular Sporocyte: diploid cell that becomes 4 haploid cells after mitosis Sporophyll: modified leaf that bears sporangium Sporophyte: spore-producing phase of life cycle Springwood: Stamen: pollen-producing structure of flower, consists of anther and filament Starch: Stele: central cylinder of tissues in a stem or root; consists of xylem and phloem Stigma: pollen receptive area of pistil Stolon: stem that grows vertically below surface; relatively long internodes Stoma: minute pore in epidermis in leaves; flanked by guard cells that regulate opening/closing and regulate gas exchange and transpiration Stratification: Strobilus: aggregation of sporophylls on common axis; resembles a cone Style (of pistil): connects stigma and ovary Suberin: fatty substance found in cell walls of cork and Casparian strips of endodermal cells Succulent: Summerwood: Suspensor (of plant embryo): Sustainability: Symbiosis: intimate association between 2 dissimilar organisms that is mutualistic or parasitic Synergids: Tendril: slender structure that coils on contact, modified leaf, helps with climbing Thigmotropism: Thorn: pointed specialized stem Tracheid: xylem cell that is tapered on ends and has thick walls containing pits Trichome: Triploid: having 3 nuclei Tube cell: Tuber (Stem): swollen fleshy underground stem Turgor movements: movement that results from changes in internal water pressure from osmosis Vascular bundle: strand of tissue composed mostly of xylem and phloem and enveloped by bundle sheath Vascular cambium: narrow, cylindrical sheath of cells that produce xylem and phloem in stems and roots Vascular tissue: xylem + phloem Vegetative cell (of pollen): any of the cells of a plant or animal except the reproductive cells; a cell that does not participate in the production of gametes Vessel element: single cell of a vessel Vitamin: complex organic compound produced by photosynthetic organisms; various vitamins are essential to facilitate enzymes reactions in living cells Whorl: (in a flower) each of the sets of organs, especially the petals and sepals, arranged concentrically around the receptacle Wild type: the phenotype for a character most commonly observed in natural populations, such as red eyes in fruit flies. mutant phenotypes: traits that are alternatives to the wild type such as white eyes Window leaf: Succulent desert plants of Africa. Leaves buried in ground, except for exposed end, end has transparent, thick epidermis and transparent water storage cells underneath, allows light into leaf, while buried leaves keep plant from drying out. Xylem: tissue through which most water and dissolved minerals utilized by plant are conducted Zone of cell division (Root): Zone of cell elongation (Root): Zone of cell maturation (Root): root hairs are only here! Zygote: product of union of 2 gametes
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