植物学及园艺学英文版 botany and horticulture 59

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1、Transpiration1.DefinitionTranspirationistheevaporationofwaterfromtheaerialpartsofplants.Ofallthewaterplantabsorbs,over95-99%istranspiredtotheairaswatervapor.4.Fromwherewateristranspired?AerialpartsofwholeyoungplantLenticels(lenticulartranspiration)0.1%Cutin(cuticulartranspiration)3%~10%S

2、tomatum(stomataltranspiration)~90%Whatismostlikelyleavingthroughthestomataoftheleafpicturehere?Water(H2O)Whatisthisprocesscalled?StomatalTranspirationCuticleCuticleMesophyllStomataGuardcellsPreventswaterlossSiteofphotosynthesisOpeningsallowgasesandwatertomoveinandoutofleafOpenandclosethe

3、stomataStomataltranspirationStomaOpenStomaClosedGuardCellsStomaImportanceoftranspirationGuardCellsCO2O2H2OWhatgoesin?Whatgoesout?WhatprocessinvolvesusingCO2andH2OreleasingO2asawasteproduct?PhotosynthesisWhatistheplantusingthisprocesstomake?Carbohydrates-glucoseIftheplantneedswaterforphot

4、osynthesis,whyiswatercomingoutofthestoma?StomaOpenStomaClosedFunctionofStomataGuardCellsThesestomata(leafopenings)naturallyallowwatertoevaporateout.Whywouldtheplantclosestomatawithguardcells?Preventexcesswaterlossthroughtranspiration.(conservewater)Sowhatisthepointofhavingstomata?Allowsg

5、asexchangeforphotosynthesisHowdotheguardcellsreacttotheavailabilityofwater?Dry–guardcellsCLOSElotsofH2O–guardcellsOPENhttp://www.ualr.edu/~botany/images.htmlFunctionofGuardCellsGuardCellsGuardcells:cellsthatopenandclosethestomaStomata:openingsinleaf’ssurface;whenopen:GASEXCHANGE:AllowsCO

6、2in&O2outofleafTRANSPIRATION:Stomata5.CharacteristicsofguardcellsGuardcellpropertiesandtheirrelationshipwithstomatalcontrolThicknessofCWvariesintheventralanddorsalpartoftheguardcells.Containschloroplastandcanperformlightreaction.(notdarkreactionforthelackofkeyenzymes)Structurallyisolated

7、fromepidermalcellsforthelackofplasmodesmata(waterandionstransmitonlythroughcellularpathway,thushelpstobuildupwatergradient)Littlevolume,littleamountofwaterabsorptionorlosscontrolsstomtalaperture.6.Mechanismofstomatalopening----K+absorptiontheoryH＋lightK＋H＋K＋MalMal－＋H+VPM