PlantEnvironmentalStressPhysiologyFanHaiPlantEnvironmentalStressPhy1WhatisPlantStressPlantstressistheadversereactionofplantstoenvironmentalconditionsthatareunfavorabletogrowth,suchaslackofsufficientnutrients,inadequatewatering,flooding,highorlowtemp.,diseaseorinsectinfestation.WhatisPlantStressPlantstre2StressBioticstresspathogenmicrobesinsectsallelopathyAbioticstresswaterTemp.lightdroughtfloodingHightemp.Lowtemp.：chilling,freezingphotoinhibitionUV

damagechemicalsSalinityAlkalinityInsecticide,herbicideAirpollutionStressBioticstresspathogenmi3PlantstressesgreatlydiminishcropyieldsBioticandabioticstressescanreduceaverageproductivityby65%~87%Plantstressesgreatlydiminis4Table:Averageyieldsandrecordyieldsof8majorcropsCropRecordyieldAverageyieldAveragelossesAbioticlosses(%ofrecordyield)BioticAbioticCorn19300460019521270065.8Wheat1450018807261190082.1Soybean73901610666512069.3Sorghum20100283010511620080.6Oat106001720924796075.1Barley114002050765859075.4Potato9410028300177755090054.1Sugarbeet12100042600171006130050.7Table:Averageyieldsandreco5WhatisStrainStrainisthebiologicchangesofplantsundertheinfluenceofplantstress.Straincanbeelasticorplasticdependingonthedegreeandlastingtimeofstress.Elasticstrain:recoverable,temporaryPlasticstrain:non-recoverable,permanentWhatisStrainStrainisthebi6I.DamagesofstresstotheplantstressPrimarydamageSecondarydamagePrimarydirect-damagePrimaryindirectdamage（injurytotheplasmalemma）（dysfunctionofmetabolism）（e.g.waterstressinsaltstress）I.Damagesofstresstothepl7I.DamagesofstresstotheplantBio-membraneChangeinmembranephaseChangeinmembraneconstituentsChangeinmembranepermeabilityI.Damagesofstresstothepl8PhotosynthesisDecreaseinPnDecreaseinstomatalapertureDecreaseinFv/FmDecreaseinquantumyieldPhotosynthesis9RespirationChangeinrespirationpathE.g.TurnEMP-TCApathwaytoPPPunderdrough,pathogenandwoundingstress.Decreaseinrespirationrateunderfreezing,hotandfloodingstressIncreaseinrespirationrateunderwoundingandpathogenstressUnderchillinganddroughtstress,therespirationrateincreasefirstandthendecreaseRespiration10ChangesofphytohormonelevelDecreaseinIAA,CTK,GBSignificantincreaseinABAIncreaseofEthunderfloodingChangesofphytohormonelevel11Oxidativestressinducedbyreactiveoxygenspecies(ROS)Reactiveoxygenspeciesarehighlyreactivemoleculescontainingatomoxygen.Itmainlyinclude4species:O2.-,·OH,H2O2and1O2

ROScanattackchloroplast,mitochondriaandotherorganelles.ROScanalsoattackmembranebycausingmembraneperoxidation.Oxidativestressinducedbyre12II.PlantsRespondtoStressinSeveralDifferentWaysEnvironmentalStressStressresponseToleranceAvoidanceEscapeII.PlantsRespondtoStressi13StressEscape:Plantavoidtheinjuryofstressbyregulatingitslifecycletoavoidmeetingwithstress.E.g.someshort-lived,desertephemeralplants

germinate,growandflowerveryquicklyfollowingseasonalrains.Theythuscompletetheirlifecycleduringaperiodofadequatemoistureandformdormantseedsbeforetheonsetofdryseason.StressEscape:Plantavoidthe14Stressavoidance:plantsavoidtheinjuryofstressbybuildingupabarriertopreventstressfactorsenteringtheplant.E.g.alfafasurvivedryhabitatsbysendingdowndeeprootsystemsthatpenetratethewatertable.Salt-secretionhalophytessecretethesaltsoutfromtheleafthusreducesaltcontentintheleaf.Stressavoidance:plantsavoid15Stresstolerance:Plantsadapttothestressenvironmentbyregulatingtheirmetabolismandrepairthedamagecausedbystress.E.g.HighlysalttoleranthalophytessuchassuaedasalsasurvivesaltyhabitatbymanystrategiessuchashighROSscavengingability,highosmoticadjustmentability,highioncompartmentalizationabilityandsoon.Stresstolerance:Plantsadapt16Adaptationvs.AcclimationAdaptationandacclimationbotharemeansofachievingtolerancetoaparticularstress.Adaptationreferstoheritablemodificationsinstructureorfunctionthatincreasethefitnessoftheorganisminthestressfulenvironment.e.g.CAMplantstodesert.Acclimationreferstononheritablephysiologicalmodificationsthatoccuroverthelifeofanindividual.Thesemodificationsareinducedbygradualexposuretothestress.E.g.slowdryingincreasesthedroughtresistanceofplants.Theprocessofacclimationisknownashardening.Adaptationvs.AcclimationAdap17Howplantsgetadaptedtostress?OsmoticadjustmentStressproteinsScavengeROSSynthesisABACross-adaptationHowplantsgetadaptedtostre181.OsmoticadjustmentWaterdeficitcanbeinducedbymanyenvironmentalconditionsDroughtSalinityColdtemperatureOsmoticadjustmentisabiochemicalmechanismthathelpsplantstoacclimatetodrought,salinityetc.Osmoticadjustmentisanactiveprocessofincreasingthenumberofsoluteparticlesintheplantthatresultinginareducedosmoticandwaterpotentialandenablestheplanttoabsorbwaterindroughtandsalinehabitat.1.OsmoticadjustmentWaterdef19植物逆境生理課件20CompatiblesolutessharespecificbiochemicalattributesHighlysolubleLowmolecularweightDonotinterferewithcellularmetabolismNeutrallychargedatphysiologicalpHMainlydistributedinthecytosol,notvacuoles

Compatiblesolutessharespeci21MostcompatibleosmolytesareAA,QACSorpolyalcoholsMostcompatibleosmolytesare22SomecompatiblesolutesmayserveotherprotectivefunctionsinadditiontoosmoticadjustmentMinimizingtheperturbingimpactofionsProtectingenzymes(pro,glycinebetain)ScavengingROS(pro,mannitol,sorbitol)Somecompatiblesolutesmayse232.StressproteinsHSPs(Heatshockproteins)CRP(Coldregulatedproteins)anaerobicpeptidesLEAs(lateembryogenensisabundantproteins)OsmotinPathogenesis-relatedproteins2.StressproteinsHSPs(Heatsh243.ScavengingROSEnzymes：SOD（superocidedismutase)CAT(Catalase)POD(AscorbicacidPeroxidase)Oxidants：caroteneVitEDMSOVitCGSH3.ScavengingROSEnzymes：254.ABA-stresshormoneKeepmembranestabilityPromotesynthesisofosmolytesReducewaterlossIncreasewaterconductivity4.ABA-stresshormoneKeepmemb26Cross-adaptationCross-adaptationmainsexposureofanorganismtoagivenadverseenvironmentmodifiesitsresponsetootheradversefactors.E.g.exposureofplantstovariousstressessuchaschillingtemperature,heat,drought,andradiationconferredresistancetootherstresses.Cross-adaptationCross-adaptati27Causesofcross-adaptationABAisinducedundermanystresses.Stressinducesmanystressproteins,andstressproteinfunctionsinmanystresses.OsmolytesareinducedbymanystressesMembranechange.ROSscavengingsystemisactivated.Causesofcross-adaptationABA28III.FreezingStressFreezinginjuryiscausedbylowtemp.<0℃SupercoolingIII.FreezingStressFreezingi29IntercellularcrystallizationIcecrystalsformbetweencells.IntracellularcrystallizationIcecrystalsforminthecell.Intercellularcrystallization30FreezingInjury:Directinjury:injurybycrystalformationIndirectinjury:dehydration,suffocatingInjurymechanism:MembraneinjuryMechanicalinjury-SHtheoryFreezingInjury:31植物逆境生理課件32Strategiesofincreasingplantfreezingtolerance:LowerwatercontentReducephotosynthesisIncreaseABA/GBDormantIncreaseosmolytesAlltheabovecanbeattainedbycoldhardeningStrategiesofincreasingplant33IV.ChillingStressCausedbylowtemp.>0℃DamageMembranephaseRootwaterabsorptionabilityDysfunctionofrespiration,accumulationofethanol.DysfunctionofmetabolismIV.ChillingStressCausedbyl34Mechanismofchillinginjury:membranephasetransition:LCphase→→GelphaseMechanismofchillinginjury:35Liquidcrystallinephase.Thetypicalphaseinbiologicalmembranes.ThelipidshavebothlateralandkineticmotionandcontainmembraneproteinsGelphase.ThemembranelipidshavelesskineticenergyandlateralmotionthanintheliquidcrystallinephaseresultinginaregularspacingbetweentheacyltailsLiquidcrystallinephase.The36Strategiesofimprovingplantchillingtolerance:IncreaseIUFA(indexofunsaturatedfattyacid),whichleadstothedecreaseofphasetransitiontemp.Synthesisofchilling-tolerantisoenzymes.Strategiesofimprovingplant37V.DroughtStressDroughtstressincludes:Soildrought,norainforlongtimeandno-availablewaterinthesoil.

Airdrought,RH<20%inatmosphere，transpiration>>waterabsorption.Iflonger,soildroughtoccurs.V.DroughtStressDroughtstres38Symptomsinplantfacingtodrought：stun,redcolorinbase，smallcellandleafarea，leafyellowishandabscission.Youngleavesor/andreproductiveorganswilttodeath.Symptomsinplantfacingtodr39Mechanismsofdroughtstress:MembranedamageMetabolicdisorder:WaterredistributionintheorganPhotosynthesisreductionRespirationrisesthendropsDecreaseinnuclearacidsandproteins

AccumulationofprolineABAaccumulationMechanicaldamageFormationofS-SMechanismsofdroughtstress:40StrategiesofincreasingdroughtresistanceStressavoidance:absorptionofwater,declinationoftranspirationandincreaseinwatertransportation.DevelopedrootsystemandhigherratioofroottoshootThickleaf,smallerleafareaandthickcuticleAccumulationofABAandstomatalcontrolStresstoleranceOsmoticadjustmentChangeofphotosyntheticpathwayStrategiesofincreasingdroug41VI.FloodstressInjuryofflood:(Secondaryinjury)Anaerobicstress:anaerobicrespiration→ethanolEthyleneevolvingVI.FloodstressInjuryoffloo42(1)InjuryinmorphologyandanatomybyO2deficiency：growth↓，leafyellowish(nutritiondeficiency），epinasty（Eth),stemhollow(tissuedegradationcausedbyEth）.(2)InjuryinmetabolismbyO2deficiency，photosynthesis↓——stomatalblock,inhibitionofCO2entrance.Anaerobicrespiration↑，toxicants:alcohol，acetaldehyde，NH3，lactate,H2S(1)Injuryinmorphologyanda43(3)Nutritiondisorder：absorption↓，soilN、P、K、CalossbutH2S、Fe、Mn↑，microele