1Plant Hormones, Constituents,& NutritionBio 1B, Fall ’06Professor Carlson2Lab AssignmentDue in last Plant LabAssignment graded by GSI each labDescribe the following information for 10 different foodsyou have eaten:1) Name of food2) Major group this food comes from: Angiosperm(Monocot or Eudicot), Gymnosperm, or Protist (e.g., redalgae, brown algae), Cyanobacteria (e.g., Spirulina)3) What plant part is consumed (e.g., leaf, stem, root,flower, fruit, seed)4) What plant tissue and/or cell type is consumed3Plant Hormones/ChemicalCommunication (Table 39.1)Gibberellic Acid (Table 39.1, Fig. 39.10-11)– Seed germination (Fig. 39.11)– Bud germination– Stem elongation– Flowering/Fruiting (Fig. 39.10)(Gibberellic Acid was originally isolated fromthe fungus Gibberella fujikuroi, which is aplant pathogen on rice that resulted inunusually long shoots)4Plant Hormones/ChemicalCommunication (Table 39.1)Auxin (indole acetic acid) (CampbellTable 39.1, Fig 39.7)– Apical dominance– Phototropism– Stem/cell elongation (Fig. 39.8)– Gravitropism5Plant Hormones/ChemicalCommunication (Table 39.1)Cytokinins (Table 39.1, Fig. 39.9)• Promote cell division & lateralbud outgrowth• Inhibit leaf senescence6Plant Hormones/ChemicalCommunication (Table 39.1)Brassinosteroids (Table 39.1)• Steroid hormone• Supports growth of xylem• Supports elongation of stems & pollen tubes• Inhibits leaf abscission7Plant Hormones/ChemicalCommunication (Table 39.1)Abscisic Acid (ABA) (Table 39.1)– Inhibits growth/stem elongation– Supports seed dormancy (Fig. 39.12)– Inhibits seed germination– Closure of stomata in response to waterstress8Plant Hormones/ChemicalCommunication (Table 39.1)Ethylene (Table 39.1)– Promotes fruit ripening– Promotes leaf abscission (Fig. 39.16)– Promotes senescence– Inhibits stem elongation (Fig. 39.13)– Inhibits gravitropism9Plant defense mechanismsHormones that Respond to Tissue Damage andTrigger Plant Defenses• oligosaccharins• jasmonates• systemin• salicylic acid10Plant defense mechanismsPhytochemical repel herbivores/microbes– Oils from variety of herbs & spices repel insects– Pine sap inhibits insect pests (e.g., bark beetles)– Tannins & resins concentrate in heartwood of treesto prevent insect & microbial infestation and rotting– Many alkaloids (e.g., caffeine, nicotine, morphine,and cocaine) repel herbivores & microbes1112131415Plant defense mechanismsBarriers to Entry:• Cuticle (Fig 35.17): matrix of cross-linkedlipid molecules impregnated with extremelylong-chained lipids• Spines, thorns, & prickles (Fig 35.7b)16171819Nutrient AcquisitionHeterotrophs: obtain nutrients from otherorganisms– animals– fungiAutotrophs: produce own food throughphotosynthesis– green plants20Photosynthesis (Figs 10.3, 10.10, page 183)• Occurs in chloroplasts in green plant tissues• Leaf parenchyma cells contain 40-50 chloroplasts• Chlorophyll pigments in plants• convert energy from sunlight to chemical energy inthe form of ATP & NADPH (an electron carrier)• Carotenoids (carotene and xanthophylls):absorb wavelengths of light that are not absorbed bychlorophyll and extend the range of wavelengths thatcan drive photosynthesis212223PhotosynthesisEquation6CO2 + 12H2O + light energy !C6H12O6 (glucose) + 6O2 + 6H224Photosynthesis 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)25Types of PhotosynthesisC3 plants use Calvin cycleAdaptation to Dry Environments–C4 plants–CAM plants26C3 plants (Fig. 10.18)• Calvin cycle takes place in each cell(Calvin was a professor at UC Berkeley!!)• Use rubisco enzyme for initial fixation ofcarbon• The CO2 is initially fixed into threecarbon sugars27Adaptation to DryEnvironmentsC4 plants (Fig 10.19, 10.20)• certain cells in the leaf sequester CO2• use PEP carboxylase for initial fixation of carbonto produce 4-carbon organic acids• favored in dry climates because it enhancesphotosynthetic efficiency by limiting the loss ofcarbon and ATP to photorespiration28Adaptation to DryEnvironmentsCAM Plants (Fig 10.20)• succulents that live in conditions of high lightintensity and water stress ! stomata are closedduring the day to prevent water loss• largely depend on night-time accumulation ofCO2• store huge quantities of CO2 in the form ofsugars and sequester them in vacuoles• during the day, these sugars are metabolized torelease CO2 and feed into Calvin cycle29Gas 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 cells3031Gas 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 fromatmosphere3233CO2 in Atmosphere & GlobalWarming" fossil fuel burning & deforestation in past 100years! " atmospheric CO2" atmospheric CO2 contributes to global warmingPhotosynthesis by green plants! removes CO2 from the atmosphere! sequesters carbon in wood34Sugar produced by photosynthetic organisms! fuels cellular respiration and growth of plant• sugars are typically stored in the form of starch(long chains of glucose molecules)• transported in the form of the disaccharide,sucrose (glucose attached to fructose) ormonosaccharide (glucose or fructose)Photosynthetic organisms are eaten by animalsand fungiDirectly or indirectly, many organisms get theirenergy from photosynthesis35Plant Pigments & PhotosynthesisCarotenoids–Carotenes (e.g., beta-carotene in carrots; lycopene in tomatoes)–Xanthophylls (e.g, zeaxanthin which gives corn yellow color)Carotenoids in chloroplasts–extend range of wavelengths that drive photosynthesis–Protect
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