1Plant Form & FunctionBio 1B, Fall ’07Professor Carlson2GerminationGermination begins with the uptake of water by theseed which activates enzymes that breakdown storedproteins, lipids, and carbohydrates into smallermolecules to be used by growing regionsGibberellic Acid is a hormone hormone that supports seedgerminationWhen the radicle (root) emerges from the seed and beginsto push into the ground, germination is completeSeedling is established when photosynthesiscommences3Germination• Gibberrelic Acid hormone supportsseed germination• Abscisic Acid hormone inhibitsseed germination and supportsseed dormancy45Primary plant body morphology(Figs. 35.2, 35.8, 35.10, 35.11, 35.12, 35.15, 35.18, 35.29 Lab manualFigs. 4.1, 4.2, 4.3, 4.4, 4.5)•Primary growth results in increase in length of stem axis•Growth initiated at tips (root & shoot apical meristems)•Apical meristems–at tips of shoots & roots–zones of high cell mitotic division activity & new cell production•Shoot apical meristems produce lateral appendages(leaves & axillary buds)•Axillary buds produce lateral shoots or branches thathave their own meristem at their tips and grow very muchlike the primary shoot axis6Plant Hormones/ChemicalCommunication (Table 39.1)Auxin (indole acetic acid) (CampbellTable 39.1, Fig 39.7)– Apical dominance by supportingactivity of apical meristems– Phototropism (shoot growth)– Gravitropism (root growth)– Stem/cell elongation (Fig. 39.8)7Plant Hormones/ChemicalCommunication (Table 39.1)Gibberellic Acid (Table 39.1, 39.10-11)– Seed germination (Fig. 39.11)– Bud germination– Stem elongation– Flowering/Fruiting (Fig. 39.10)(Gibberellic Acid was originally isolatedfrom the fungus Gibberella fujikuroi,which is a plant pathogen on rice thatresulted in unusually long shoots)891011121314Shoot(Fig 35.2, 35.8, 35.10, 35.11, 35.15, Lab Manual Figs 4.1, 4.3)Terminal budLateral budsNode: site of lateral buds on shootInternode: distance between two nodes15Plant Hormones/ChemicalCommunication (Table 39.1)Cytokinins (Table 39.1, Fig. 39.9)• Promote cell division & lateralbud outgrowth• Inhibit leaf senescence16Stem elongation supportedby following hormones:• Gibberellic Acid• Auxin• Brassinosteroids17Stem elongation inhibitedby following hormones:• Abscisic Acid• Ethylene1819Leaf(Fig 35.2, 35.5b, 35.6, 35.7, 35.8, 35.17, 35.29)• Leaf: Blade with petiole (leaf stalk)• Celery: the petiole is the edible plant part• Lettuce: the blade of the leaf is the edible plantpart• Wide variety of leaf shapes & sizes in responsedifferent environments• Leaf blade is primary site of photosynthesis20Leaf Abscision• Promoted by ethylene• Inhibited by brassinosteroids2122Leaf(Fig 35.2, 35.5b, 35.6, 35.7, 35.8, 35.17, 35.29)Features of photosynthetic leaves:– epidermis (outer covering layer) consistsof specialized guard cells– internal parenchyma cells whichcompose main photosynthetic region– vascular tissue (“veins”) specialized fortransport of water & photosynthate23Leaf CuticleCuticle (Fig 35.17): matrix ofcross-linked lipid moleculesimpregnated with extremelylong-chained lipids functions asa protective layer around theoutside of the leaf2425Nutrient AcquisitionHeterotrophs: obtain nutrients from otherorganisms– animals– fungiAutotrophs: produce own food throughphotosynthesis– green plants26Photosynthesis (Figs 10.3, 10.10, page 183)• Occurs in chloroplasts in green plant tissues• Leaf parenchyma cells contain 40-50chloroplasts• Chlorophyll pigments in plants• convert energy from sunlight to chemicalenergy in the form of ATP & NADPH (anelectron carrier)• Carotenoids (carotene and xanthophylls):absorb wavelengths of light that are not absorbedby chlorophyll and extend the range ofwavelengths that can drive photosynthesis2728PhotosynthesisEquation6CO2 + 12H2O + light energy !C6H12O6 (glucose) + 6O2 + 6H229Photosynthesis Equation6CO2 + 12H2O + light energy ! C6H12O6 + 6O2 + 6H2O (C6H12O6 = glucose)Simplest Form of Photosynthesis EquationCO2 + H2O + light energy ! CH2O + O2 + H2OLight-dependent reactionsLight energy + H2O ! chemical energy (ATP, NADPH) + O2(oxygen in O2 derived from oxygen in H2O)Light-independent reactions (Calvin Cycle)Chemical energy (ATP, NADPH) + CO2 ! CH2O(Carbon in sugar is derived from carbon in CO2)303132Gas exchangebetween atmosphere and plant viastomata in leavesStoma (stomata plural): guard cells & pores (Fig 10.3)Guard cells: pair of bean-shaped cellsPore: opening between guard cellsAbscisic Acid (ABA) causes stomata to close duringtimes of low water availability33Gas exchange between atmosphere & plantvia stomata in leaves• O2 produced by plant released out of stomata pores intoatmosphere where it is available for humans & animals tobreath• H2O released out of the pores via evapo-transpiration• in some species (e.g., coastal redwoods & Douglas Firs) duringhigh fog conditions, H2O can be absorbed from the air into theleaf through the stomata pores to provide H2O for the plant• During photosynthesis when CO2 levels within leaf fall belowoptimal levels, the stomata open & CO2 diffuses in fromatmosphere34CO2 in Atmosphere & GlobalWarming" fossil fuel burning & deforestation in past 100 years! " atmospheric CO2" atmospheric CO2 contributes to global warmingPhotosynthesis by green plants! removes CO2 from the atmosphere! sequesters carbon in wood3536Sugar produced by photosynthetic organisms! fuels cellular respiration and growth of plant• sugars are typically stored in the form of starch (longchains of glucose molecules)• transported in the form of the disaccharide, sucrose(glucose attached to fructose) or monosaccharide(glucose or fructose)Photosynthetic organisms are eaten by animals and fungiDirectly or indirectly, many organisms get their energy fromphotosynthesis37Plant Pigments &PhotosynthesisCarotenoids:–Carotenes (e.g., beta-carotene incarrots; lycopene in tomatoes)–Xanthophylls (e.g, zeaxanthin whichgives corn yellow color)38Plant Pigments & PhotosynthesisCarotenoids in chloroplasts:– extend range of wavelengths thatdrive photosynthesis– protect chlorophyll by acting asanti-oxidant and destroy free radicalsthat damage the chlorophyllmolecules (beta-carotene also works abeneficial anti-oxidant in humans)39Plant Pigments & PhotosynthesisDuring most of year the carotenoids arenot visible in the leaves because thechlorophyll pigments cover them up.In fall, as the deciduous leaves
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