Abstract:

The diurnal photosynthesis and photoinhibition in the photoperiod-sensitive genic male-sterile rice (Oryza sativa L.), Nongken 58S (NK58S), were investigated in this paper. From 06:00 to 09:00, no remarkable photoinhibition occurred, and the down-regulation of photosynthesis might be due to the running of xanthophylls cycle. From 10:00 to 12:00, the specific energy flux for dissipation (DI_o/RC) and the net rate of reaction centers (RCs) closure (dV/dt_o) were increased, while the probability of electron transport at the acceptor side (y_o) and the density of active RCs (D_o) were decreased. These indicated that the photoinhibition of NK58S was exacerbated with the inactivation of PSⅡ RCs. Fluorescence dark relaxation analysis and inhibitor treatment suggested that all of state transition, xanthophyll cycle and inactivation of PSⅡ RCs could contribute to protect NK58S against photodamage. Compared with the inactivation of PSⅡRCs, xanthophyll cycle had an immediate response to high light stress, which functioned mainly in the period of relatively low light intensity. However, the inactivation of PSⅡ RCs played an important role in protecting the remaining active RCs when xanthophyll cycle was saturated.

Key words: photoperiod-sensitive genic male-sterile rice, Nongken 58S, JIP test, photoinhibition, reaction center inactivation, D1 protein turnover, xanthophylls cycle