Relationship of Nitrogen Utilization and Activities of Key Enzymes Involved in Nitrogen Metabolism in Rice Under Water–Nitrogen Interaction

The objective of this study was to disclose the effects of water-nitrogen (N) interaction on activities of N metabolism enzymes and N absorption and utilization in rice (Oryza sativa L.). The hybrid rice Gangyou 527 was grown under 3 water treatments namely submerged irrigation (W1), alternation irrigation (W2), and dry cultivation (W3) and 4 N levels with N application rate of 0 (N0), 90 (N90), 180 (N180), and 270 kg ha−1 (N270). The activities of nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT), and endopeptidase (EP) were measured at tillering, elongation, heading, and maturity stages to analyze the correlations between activities of these enzymes in functional leaves and the N absorption and utilization in plant or grain yield. There was an obvious interaction between irrigation method and N application level. Compared to other irrigation treatments, W2 promoted the N uptake of plant from tillering to heading, the N dry matter production efficiency (NMPE), and the N production efficiency (NPE). W2 coupling with N180 showed the best water-introgen interaction, which enhanced the enzyme activities in relation to N metabolism, the grain yield, and the N use efficiency. Excessive N application (N270) resulted in negative influences on water-nitrogen interaction, such as slow increase of NR, GS, and GOGAT activities, reductions of N agronomy efficiency (NAE) and N recovery efficiency (NRE), and decrease of yield. The enzyme activities were positively correlated with the indices for N uptake and utilization at various stages and the grain yield at maturity. The GS activity in function leaf was proposed as a candidate indicator for N uptake and accumulation at various growth stages, and the activities of NR, GS, GOGAT, and EP in flag leaf at heading stage as candidate indicators for rice yield and NMPE, NPE, NAE, and NRE.

摘 要以杂交稻冈优527为材料, 设“淹水灌溉”(W1)、“前期湿润灌溉+孕穗期浅水灌溉+抽穗至成熟期干湿交替灌溉”(W2)和“旱种”(W3) 3种灌水及不同的施氮量处理, 研究对水稻氮代谢酶活性及氮素吸收利用的影响, 并探讨各生育期水稻氮代谢酶活性与氮素吸收利用及产量间的关系。结果表明, 水与氮对水稻各生育期氮代谢酶活性及氮素吸收利用有显著互作作用, W2相对于其他灌水处理有助于拔节至抽穗期水稻吸氮量的增加, 提高氮素干物质生产效率及稻谷生产效率, 而且与施氮量为180 kg hm−2耦合能达到提高氮代谢酶活性、增产、提高氮肥利用效率的目的, 为本试验最佳的水氮耦合运筹模式；施氮量达270 kg hm−2时水氮互作优势减弱, 不利于3种灌水方式下硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)活性的提高, 还会导致产量及氮效率的下降。相关分析表明, 水氮互作下各氮代谢酶活性与氮素利用特征及产量间存在显著或极显著的相关性, 据此可将各生育期功能叶GS活性作为准确判断水稻各生育期氮素积累量的指标；并可将抽穗期剑叶中NR、GS、GOGAT及内肽酶(EP)活性作为综合评价水稻产量及氮效率的指标。