Abstract: To study the effects of salicylic acid (SA) on the D₁ protein phosphorylation and PSⅡ performance in wheat (Tritivum aestivum L.) leaf chloroplasts under high temperature and high light, the wheat leaves at grain-filling stage were sprayed with SA solution (0.5 mmol·L^-1) or water (as control), and then subjected to 35 ℃ and 1 600 μmol·m^-2·s^-1 for various hours. The changes in electron transport rate (ETR), net photosynthetic rate, chlorophyll fluorescence parameters, and relative amount of phosphorylated and nonphosphorylated D₁ protein in thylakoid membrane were compared. The results showed that foliar spraying SA effectively inhibited the degradation of D₁ protein under high temperature and high light stress, and maintained the D₁ protein phosphorylation, ETR of whole chain and PSⅡ, F_v/F_m (the maximal photochemical efficiency of PSⅡ), Ф_PSⅡ (the actual photochemical efficiency of PSⅡ), q_P (the photochemical quenching coefficient), and P_n (net photosynthetic rate) at a higher level, indicating that exogenous SA could mitigate the damage effect of high temperature and high light on wheat leaf photosynthetic apparatus and benefit PSⅡperformance via regulating the turnover of D₁ protein in chloroplasts.

Key words: photosynthetic characteristics, shading, chlorophyll fluorescence, Corydalis, chlorophyll