Acold-tolerantcultivar,Xiangnuo1,andacold-sensitivecultivar,IR50,wereusedtostudytheinfluenceofchillingonphotosyntheticrateandchlorophyllfluorescenceparametersinriceseedlings.Thephotosyntheticratesdeclineddramaticallyduringchilling,anddecreasedby48.7%and67.5%inXiangnuo1andIR50seedlings,respectively,afterbeingsubjectedtochillingtreatmentfortwodays.ChlorophyllfluorescencemeasurementsshowedthatrelativelyhigherqPandqNPinXiangnuo1weremaintainedtodissipatetheredundantexcitationenergyandprotectthereactioncentersfromchillinjury;accordingly,redundantexcitationenergyaccumulatedlessinthereactioncenters,andantennasystemswerelessinjuredbychillinginXiangnuo1.Onthecontrary,inIR50,qPandqNPdeclinedrapidlywhileExincreased,asthechillingpersisted.ThisresultindicatedthatthereactioncentersandantennasystemsinIR50weredamagedseverelybychilling,whichledtothelowerphotosyntheticrate.
