Effects of Leaf Chilling on Thylakoid Functions, Measured at Room Temperature, in Cucumjs sativus L. and Oryza sativa L.

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Photosynthetic functions in leaves of cucumber (Cucumis sativus L.) and rice (Oryza sativa L.) were examined before and after various chilling treatments. Cucumber leaves lost the capacity for the photosynthetic oxygen evolution after chilling at 0℃ in the dark for 48 h. Thylakoids isolated from such leaves were not able to reduce dichloroindophenol (DCIP), but the addition of diphenylcarbazide (DPC), an electron donor to PS II, restored the ability to reduce DCIP, indicating that the site of damage is in the water-splitting machinery of PS II. In moderate light (500 μmol quanta・m^<-2>・s^<-1>), chilling of cucumber leaves at 5℃ for 5 h was sufficient to induce the complete loss of the capacity for photosynthetic oxygen evolution. Electron transport rates measured in thylakoids were unaltered, but thylakoids were totally permeable to protons. Since the addition of dicyclohexylcarbodiimide (DCCD) restored coupling and the capacity for proton uptake, the primary site of damage was deduced to be in the ATPase. In rice, both chilling treatments had barely any effect on thylakoid functions, although some negative effects was apparent in photosynthesis in leaves.
日本植物生理学会の論文