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土壤水分胁迫下红豆草的水分生理与光合特性.docx

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土壤水分胁迫下红豆草的水分生理与光合特性 Introduction Redclover(TrifoliumpretenseL.)isapopularforagecropwidelycultivatedintemperateandsubtropicalregions.However,itisoftensubjectedtosoilwaterstress,whichadverselyaffectsitsgrowthandyield.Understandingthewaterandphotosyntheticphysiologyofredcloverundersoilwaterstressisessentialfordevelopingstrategiestoimproveitsdroughttoleranceandproductivity. Waterphysiologyundersoilwaterstress Soilwaterstressimposesadirecteffectonredcloverbyreducingthewaterabsorptioncapacityoftherootsystemandinducingwaterdeficitintheplanttissues.Undersoilwaterstress,redcloverundergoesaseriesofwaterphysiologicalchangestocopewiththewaterdeficit,suchasreducingleafwaterpotential,stomatalclosure,andincreasingroot/shootratio.Stomatalclosureplaysanessentialroleinreducingtranspirationandwaterlossundersoilwaterstress,butitalsoinhibitsCO2assimilationandphotosynthesis.Therefore,redcloverneedstomaintainabalancebetweenreducingwaterlossandmaintainingphotosyntheticactivity. Photosynthesisundersoilwaterstress Photosynthesisisoneofthemostimportantphysiologicalprocessesthatdeterminethegrowthandproductivityofredclover.Undersoilwaterstress,thephotosyntheticrateofredcloverdecreasesduetostomatalclosureandbiochemicalchanges.StomatalclosurereducesCO2diffusionintotheleafandlimitsthephotosyntheticsubstratesupplyforphotosynthesis.Atthesametime,soilwaterstressalsoimpairsthefunctionofthephotosyntheticapparatusbydecreasingtheactivityofthephotosyntheticenzymes,suchasRubisco,andalteringthephotosyntheticpigments'composition. Redclover'sresponsetosoilwaterstress Redcloverhasevolvedvariousstrategiestocopewithsoilwaterstress,suchasosmoticadjustment,antioxidantdefensemechanisms,andaccumulationofcompatiblesolutes.Osmoticadjustmentinvolvestheaccumulationofosmoticallyactivecompounds,suchassugarsandaminoacids,intheplantcellstomaintaincellturgorandwaterpotential.Antioxidantdefensemechanismsinvolvetheinductionofantioxidants,suchasascorbate,glutathione,andtocopherol,toscavengereactiveoxygenspecies(ROS)generatedun