水分和氮素对水稻叶片光合特性和氮素吸收利用有重要影响，但在干湿交替灌溉条件下，水、氮是如何影响水稻叶片和根系氮代谢酶活性、产量和氮素吸收利用仍不清楚。探明这一问题，对于协同提高产量和氮肥利用效率有重要意义。本研究以超级稻品种南粳9108为材料，大田种植，设置全生育期常规灌溉(conventional irrigation, CI)和干湿交替灌溉(alternate wetting and drying irrigation, AWD) 2种灌溉方式及5个施氮水平，不施氮(N0)、施氮90 kg hm-2 (N1)、施氮180 kg hm-2 (N2)、施氮270 kg hm-2 (N3)和施氮360 kg hm-2 (N4)。结果表明，与CI相比，AWD增加了水稻主要生育时期叶片的叶绿素a、叶绿素b、总叶绿素和类胡萝卜素含量，提高了叶片净光合速率，并显著增加了叶片中超氧化物歧化酶、过氧化氢酶、硝酸还原酶、谷氨酰胺合成酶和谷氨酸合成酶活性，显著降低了过氧化物酶、内肽酶活性和丙二醛含量，显著提高了根系中氮代谢酶硝酸还原酶、谷氨酰胺合成酶、谷氨酸合成酶和谷氨酸脱氢酶活性；AWD的产量较CI平均增加了10.4%。AWD显著提高了氮素转运量、氮素转运率、氮肥吸收利用率和氮肥偏生产力，产量和氮肥利用率均以AWD+N3处理组合的最高。因此，轻度干湿交替灌溉配合一定的施氮量，可以充分发挥水、肥效应，促进根系和叶片的氮代谢水平，提高叶片光合特性，协调地下地上部生长，有利于水稻产量和氮肥利用率的协同提高。
Soil water potential and nitrogen nutrients are the important factors affecting photosynthetic characteristics in leaves and nitrogen absorption and utilization of rice (Oryza sativa L.). Little is known, however, how synergistic the two factors under alternative wetting and drying irrigation (AWD) can be in terms of nitrogen metabolism enzyme activity, grain yield, and nitrogen use efficiencies. A field experiment was conducted using a super rice variety of Nanjing 9108 with five nitrogen levels, namely, no nitrogen applied (N0), 90 (N1), 180 (N2), 270 (N3), and 360 kg hm-2 (N4), and two irrigation regimes, namely, conventional irrigation (CI) and AWD over two years. Our results revealed significant interaction between irrigation and nitrogen levels. At the same nitrogen levels, the content of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid, net photosynthetic rate, the activities of superoxide dismutase, catalase, nitrate reductase, glutamine synthetase, and glutamic acid synthetase at main growth stages were higher in AWD than those in CI. Furthermore, the activities of nitrate reductase, glutamine synthetase, glutamic acid synthetase, and glutamate dehydrogenase in roots of rice were also increased, but the activities of peroxidase, endopeptidase, and the content of malondialdehyde in leaves were lower. AWD treatment increased grain yield by an average of 10.4% compared with CI, and also enhanced nitrogen transport capacity, nitrogen transport efficiency, nitrogen absorption, utilization efficiency, and partial productivity of nitrogen fertilizer. AWD coupled with N3 had the highest yield and nitrogen use efficiency; this treatment was the optimal water–nitrogen interaction management model in this study. These results suggest that adopting AWD with an appropriate nitrogen rate promotes nitrogen metabolism in roots and leaves and improves photosynthetic characteristics of leaves, thereby synergistically increasing grain yield and nitrogen use efficiency in rice.