Acclimation of biochemical and diffusive components of photosynthesis in rice, wheat and maize to heat and water deficit: implications for modeling photosynthesis

Abstract

[eng] heimpactofthecombinedeffectsofheatstress,increasedvaporpressuredeficit(VPD)andwaterdeficitonthephysiologyofmajorcropsneedstobebetterunderstoodtohelpidentifyingtheexpectednegativeconsequencesofclimatechangeandheatwavesonglobalagriculturalproductivity.Toaddressthisissue,rice,wheat,andmaizeplantsweregrownundercontroltemperature(CT,25◦C,VPD1.8kPa),andahightemperature(HT,38◦C,VPD3.5kPa),bothunderwell-watered(WW)andwaterdeficit(WD)conditions.Gas-exchangemeasurementsshowedthat,ingeneral,WDconditionsaffectedtheleafconductancetoCO2,whilegrowthatHThadamoremarkedeffectonthebiochemistryofphotosynthesis.Whencombined,HTandWDhadanadditiveeffectinlimitingphotosynthesis.Thenegativeimpactsoftheimposedtreatmentsontheprocessesgoverningleafgas-exchangewerespecies-dependent.Wheatpresentedahighersensitivitywhilericeandmaizeshowedahigheracclimationpotentialtoincreasedtemperature.RubiscoandPEPCkineticconstantsdeterminedinvitroat25◦Cand38◦CwereusedtoestimateVcmax,Jmax,andVpmaxinthemodelingofC3andC4photosynthesis.Theresultshereobtainedreiteratetheneedtousespecies-specificandtemperature-specificvaluesforRubiscoandPEPCkineticconstantsforapreciseparameterizationoftheph