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PHOTOSYNTHESIS Botany2 Mrs.Russell Talkwithyourtable… Wheredoesphotosynthesistakeplace? Where? Inplants—plantsareAUTOTROPHIC (selfproducing) Inleaves—Stomaandmesophyllcells Inchloroplast—usingchlorophyll (greenpigment) • Mesophyll—Betweenthe epidermislayers,contains chlorophyll(locaPonof photosynthesis) – Palisademesophyll—elongated, narrowcells,mostofphotosynthesis takesplacehere – Spongymesophyll—irregularly shapedcells,airspacethat communicatewiththestomata • Wherephotosynthesistakesplace Whyareplantsgreen? Chlorophyll • Locatedinthylakoid • Harvestenergyfromthesun – Absorbblueandred(notgreen!) Absorp8on violetbluegreenyelloworangered wavelength Howdoleaveschangecolor? • Chlorophyllpigmentsdecrease • Carotenoidpigmentsincrease(redsand yellow) • Epidermis—outermostlayer,coversenPre plant,closelypackedcells • Cu8cle—protecPvefilmcoveringthe epidermis • Stomata—poresinthecuPclewherewater andgasareexchanged,intheepidermis Stoma(pl=stomata) • Guardcells • Surroundthepore, regulatetheopening • Regulatetherateof transpiraPon 2PartstoPhotosynthesis • LightReacPons(akaLightDependent) • CalvinCycle(akaLightIndependent) LightDependentReacPons • Happensinthethylakoid • Producesenergyfromthesun – ATPandNADPH(usedlater) – Oxygenisalsoproduced(fromwaterspliXng) ETCandATPSynthesisVideo CalvinCycle • Takeplaceinthestroma • UsetheenergycreatedintheLightReacPons • Convertcarbondioxidetoglucose • Although,nodirectsunlightisused,itonly occurswhenlightisavailable(notatnight) Atnight…PhotorespiraPon • Usestarchreservestofixcarbon – C3(threecarbonmolecule) • Inareaswheresunlightintensityand temperaturesaremoderateandgroundwater isplenPful • Represent95%ofplantbiomass • Examples:Rice,barley – C4(fourcarbonmolecule) • Tropicsandsubtropics • Examples:Sugarcane,sorghum – CAM(fourcarbonmolecule) • AridcondiPons • Stomataremainshutduringthedayandopen atnight • Examples:Succulents,pineapple
