Introducing enzymes involved in photosynthesis of C4 plants into rice is supposed to enhance the photosynthesis and crop productivity.However, only a few researches showed that the photosynthesis and crop productivity has been improved by introducing phosphoenolpyruvate carboxylase (PEPC) gene into rice.In the present research, the photosynthesis in 42 lines of PEPC gene overexpressed rice was investigated.The average photosynthetic rate (Pn) of the transgenic rice lines was almost the same as that of the wild type (control) in paddy field, but it was much higher in upland field than in paddy field.Only a few transgenic lines showed higher Pn in paddy field and most of them showed higher Pn in upland field.Similar results were found in the water controlled experiment.Two transgenic rice lines with different relative activities of PEPC (10 and 25 folds) were selected to study their photosynthesis under different water potentials (0, -20, and -40 kPa).In both lines, Pn was similar with that in the wild type under normal condition (0 kPa) but much higher under drought conditions (-20 and -40 kPa).In both experiments, the transgenic lines had higher Pn under drought conditions, with a much slower decreasing rate than the wild type.These results suggested that the overexpressed PEPC could not improve the photosynthetic rate of transgenic rice plants.But the photosynthetic rate of transgenic rices declined slowly under drought condition.Therefore, it is supposed that PEPC might be involved in drought resistance to decrease the inhibition of drought stress on photosynthesis in rice.
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