Diurnal Photosynthesis and Photoinhibition of Rice Leaves with Chlorophyll Fluorescence

摘要

The diurnal photosynthesis and photoinhibition in the photoperiod-sensitive genie male-sterile rice (Oryza sativa L.), Nongken 58S (NK58S), were investigated. 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 ((ψ_o) and the density of active RCs (D_o) were decreased. These indicated that the photoinhibition of NK58S was exacerbated with the inactivation of PS II RCs. Fluorescence dark relaxation analysis and inhibitor treatment suggested that all of state transition, xanthophyll cycle and inactivation of PS II RCs could contribute to protect NK58S against photodamage. Compared with the inactivation of PS II RCs, 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 PS II RCs played an important role in protecting the remaining active RCs when xanthophyll cycle was saturated.