Photochemical efficiency of PSII and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa) under chilling temperature and strong light stress conditions

Relationships between fluorescence parameters and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) during later growth stage were studied under chilling temperature and strong light stress conditions. Results showed that D1 protein contents of PS II in photosynthetic apparatus dropped, the generation of antheraxanthin (A) and zeaxanthin (Z) of xanthophyll cycle were inhibited partly, PS II photochemical efficiency (F-v/F-m) and non-photochemical quenching (q(N)) were also decreased obviously. In addition, endogenous active oxygen scavenger-superoxide dismutase (SOD) reduced, superoxide anion radical (O-2(-)) and malondialdehyde (MDA) accumulated, as a result, photooxidation of leaves occurred under chilling temperature and strong light stress conditions. Obvious differences in the changes of the above mentioned physiological parameters between indica and japonica rice were observed. Experiments in leaves treated with inhibitors under chilling temperature and strong light conditions showed that indica rice was more sensitive to chilling temperature with strong light and subjected to photooxidation more than japonica rice. Notable positive correlation between D1 protein contents and F-v/F-m or (A + Z)I( A + Z + V), and a marked negative correlation between F-v/F-m and MDA contents were obtained by regression analysis in indica and japonica rice during chilling temperature and strong light conditions. According to the facts mentioned above, it was inferred that PS II photochemical efficiency( F-v/F-m) was the key index to forecast for the prediction of photooxidation under stress circumstances and the physiological basis were the synthetic capacity of D1 protein and the protection of xanthophyll cycle.