Photochemical efficiency of PS_and membrane lipid peroxidation in leaves of indica and japonica rice (Oryza sativa L.) under different temperates and light intensities

Abstract

Potted indica and japonica rice plants were put in phytotron with day/night temperature of 26±1ºC/22±1ºC and 11±1ºC/l0±1ºC, and the RH of 78-82%. The photoperiod was 12 h with the PFD of 350, 700, 1050 and 1400 µmol m-2 s-1, respectively, from 6:00 to 18:00 for 4 days. Xanthophyll cycle components were assayed by HPLC system. Measurements of chlorophyll fluorescence, 14C-Atrazine-bound DI protein, SOD activity, O2? forming rate and membrane lipid peroxidation product (MDA) were carried out. Results were as follows: (1) No changes in PSII photochemical efficiency (Fv/Fm) and MDA were observed, so neither photoinhibition nor photooxidation happened in indica and japonica rice under moderate temperature and medium PFD; (2) Fv/Fm dropped obviously with no change in MDA contents, and photoinhibition appeared in indica rice either under medium temperature and higher PFD or under lower temperature and medium PFD; (3) Dl protein, Fv/Fm (A+Z)/(A+Z+V), qN, and SOD activities dropped, and contents of O2? and MDA increased accordingly, and both photoinhibition and photooxidation appeared in indica and japonica rice under lower temperature and higher PD; (4) Experiment with inhibitors (SM, DTT and DDTC) under lower temperature and higher PFD showed that indica rice had a decrease in Dl protein contents, SOD activities, an inhibition in xanthophyll cycle and qN within a greater range, and a higher level of MDA, thus indica rice exhibited more distinct photoinihibition and photooxidation as compared with japonica rice. We suggested that Fv/Fm and membrane lipid peroxidation product (MDA) were the key indexes to predict and diagnose photooxidaton.