The characteristics of CO2 assimilation of photosynthesis and chlorophyll fluorescence in transgenic PEPC rice

With PEPC, PPDK, NADP-ME and PEPC+ PPDK transgenic and untransformed rice ( Orysa sativa L.), the activities of related C4 photosynthesis enzymes, the chlorophyll fluorescence parameters, CO2 exchange and other physiological i ndexes were compared, in which the physiological characteristics of PEPC tr ansgenic rice were mainly studied. The results were as follows: (i) The act ivities of PEPC in PEPC transgenic rice were 20-fold higher than those in u ntransformed rice; the light-saturation photosynthetic rates and the carbox ylation efficiency of PEPC transgenic rice were increased by 55% and 50% mo re than those of untransformed rice, respectively, while the CO2 compensati on point decreased by 27%. (ii) The PS II photochemical efficiency (F-v/F-m ) and photochemical quenching (q(P)) of transgenic PEPC rice decreased less in comparison with those of untransformed rice after the treatment with hi gh light intensity (3 h) or methyl viologen (MV), a photooxidative reagent, which demonstrated that the tolerance of PEPC transgenic rice to photoinhi bition and photooxidation was enhanced. (iii) Under the condition of high l ight intensity, the activity of RuBPCase in PEPC transgenic rice did not ob viously vary while the activity induced of carbonic anhydrase (CA) in PEPC transgenic rice increased by 1.8 fold. These results would provide some ben eficial enlightment for revealing the mechanism of high photosynthetic effi ciency and breeding with high photosynthetic efficiency in rice.