The objective of this study was to reveal transgenic rice with high expression of maize C 4-PEPC pho-tosynthetic performance under low nitrogen conditions,two rice genotypes including C 4-PEPC transgenic rice (PC) and untransgenic Kitaake rice(WT)in the pot experiments were chosen to measure their photosynthesis characteris-tics,SPAD values,PEPC,Rubisco,NR and GS activities of flag leaves at different flowering stage under different ni-trogen applications(normal nitrogen 300 kg /ha,low nitrogen 65 kg /ha)and their yield component were investigated after harvest.The results showed that the net photosynthetic rate of PC compared with WT were increased by 1 3.1 0% (P <0.05 )and 29.29% (P <0.05 ),respectively in the 1 4,28 d after flowering under low nitrogen treatment.At the same time,under low concentrations of nitrogen,relative to untransformed wild type rice,activity of Rubisco carboxylase of PC were increased by 67.86% and 52.63% (P <0.05)in the 1 4,28 d after flowering re-spectively,while activity of nitrate reductase of PC were increased 79.49% (P <0.05)and 1 7.96%.Meanwhile, activity of glutamine synthetase of PC was increased 28.48% (P <0.05)only in the 28 days after flowering com-paring with WT.But we did not find significant differences in the yield of PC and WT under low nitrogen condi-tions.Therefore,PC maintain high net photosynthetic rate by inducing the activity of carbon and nitrogen key en-zyme improvement under low nitrogen conditions.%为揭示高表达转玉米 C4-PEPC 基因水稻在低氮条件下的光合表现，采用高表达转玉米 C4-PEPC 基因水稻（PC）与原种 Kitaake（WT）为试验材料，通过盆栽试验，分别测定不同的氮素条件下（中氮300 kg ／hm2，低氮65 kg ／hm2），开花后不同天数的 SPAD 值，光合参数以及碳氮关键酶活性。并在开花后50 d 收获植株，记录产量因子。结果表明：低氮处理下的 PC 相对于 WT 来说，在开花后14，28 d，其净光合速率分别提高了13．10％（P ＜0．05）和29．29％（P ＜0．05）。同时，Rubisco 羧化酶在开花后14，28 d 时活性分别提高了67．86％和52．63％（P ＜0．05）；硝酸还原酶在14，28 d时的活性分别提高79．49％（P ＜0．05）和17．96％；谷氨酰胺合成酶仅在开花后28 d 时活性提高28．48％（P ＜0．05）。但是通过对产量进行分析，在低氮条件下，并未发现 PC 的产量与 WT 有明显差异。可见，PC 通过诱导碳氮的关键酶活性的提高维持低氮条件下高净光合速率。
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