Overexpression of phosphoenolpyruvate carboxylase (PEPC) gene in transgenic rice to improve photosynthesis and stress resistance have brought extensive interest in the world. Our previous report proved that the overexpressed PEPC alleviate drought stress inhibition on photosynthesis. In the present research, photosynthetic light curve, chlorophyll a fluorescence parameters, pigment content and reactive oxygen metabolism were studied under drought stress at flowering stage in two lines of PEPC transgenic rice plants. The results showed that under drought especially severe drought stress, net photosynthetic rate decreased dramatically under high photosynthetic active radiation (PAR) in wild type untransformed rice, while maintained unchanged in PEPC transgenic lines under high PAR even more than 1 200 umol m~2 s-1; and the photochemistry activities (Fv/Fm, ψpsii, and q?) decreased less under drought stress in both the PEPC transgenic lines. These indicated PEPC enhanced the photoinhibition tolerance of rice under drought stress. The higher zeaxanthin content under drought stress made the PEPC transgenic rice leaves disperse more light energy as heat, thus decreased the O2- producing rate in PSII. At the same time, the SOD, POD, and CAT activities were higher in PEPC transgenic rice plants under drought stress. These enzymes could effectively diminished the reactive oxygen species and reduced the membrane lipid peroxidation.%以过表达磷酸烯醇式丙酮酸羧化酶(PEPC)的水稻为材料,研究了不同程度干旱胁迫下开花期剑叶光合作用的光响应过程、叶绿素荧光参数、色素含量和活性氧代谢.结果表明,在干旱特别是重度干旱胁迫下,野生型水稻在强光下净光合速率迅速下降,而转Zmppc基因水稻没有明显的下降现象；而且表示光化学活性的叶绿素荧光参数Fv/Fm、ΦPSⅡ和qP下降程度低,说明PEPC增强了干旱胁迫下水稻抵御强光胁迫的能力.这可能是因为干旱胁迫下转Zmppc基因水稻玉米黄质含量高,光系统对过剩光能的耗散能力强,能够保护光系统免受过剩光能的伤害,从而减小O-2产生速率；同时干旱胁迫下转PEPC基因水稻抗氧化酶SOD、POD和CAT活性高,能有效清除活性氧,减轻膜质过氧化.
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