The photosynthetic function analysis for leaf photooxidation in rice

Photooxidative damage causes early leaf senescence and plant cell death. In this study, a light-sensitive rice cultivar, 812HS, and a non-light-sensitive cultivar, 812S, were used to investigate early leaf photooxidation. Leaf tips of 812HS exhibited yellowing under a light intensity of 720 μmol(photon) m^-2 s^-1, accompanied by a decrease in chlorophyll and carotenoids, but 812S was unaffected. The photosynthetic performance of 812HS was also poorer than that of 812S. The H₂O₂, O₂ ^·-, and malondialdehyde content increased sharply in 812HS, and associated antioxidant enzymes were inhibited. The degradation of core proteins in both PSI and PSII, as well as other photosynthesis-related proteins, was accelerated in 812HS. When shaded [180 μmol(photon) m^-2 s^-1], 812HS recovered to normal. Therefore, our findings suggested excess light disturbed the balance of ROS metabolism, leading to the destruction of the antioxidant system and photosynthetic organs, and thus triggering the senescence of rice leaves.