Relationship of Activities of Key Enzymes Involved in Nitrogen Metabo-lism with Nitrogen Utilization in Rice under Water-Nitrogen Interaction

Abstract

Hybrid rice Gangyou 527 was used to investigate the effects of three irrigation regimes (submerged irrigation, W 1; dry cultivation, W 3; and damp irrigation before booting stage plus shallow irrigation at booting stage plus wetting-drying alternation irrigation from heading stage to mature stage, W 2) and different amounts of N application on activities of N metabolism enzymes and N absorption and utilization in rice, and the correlation of the N metabolism enzymes activities in functional leaves with N absorption and utilization and yield at different growth stages. The results showed that there was an obvious interaction between irrigation regime and amounts of N application. Compared with other irrigation treatments, the treatment W 2 promoted the N uptake from tillering to heading, N dry matter production efficiency (NMPE) and N production efficiency (NPE). W 2 and suitable N application amount (180 kg ha -1) enhanced activities of N metabolism enzymes, yield, and nitrogen use efficiency, being the best model in this paper referred as the water-nitrogen coupling management model. Applying nitrogen 270 kg ha -1 resulted in negative effect of water-nitrogen interaction, slowing down the increase of activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT), decreasing N agronomy efficiency (NAE), N recovery efficiency (NRE), and yield. Correlation analysis indicated that there existed significantly or highly significantly positive correlations of activities of N metabolism enzymes with indices of N uptake and utilization and yield, with different correlation coefficients of different growth stages. According to the conditions above, GS activity in function leaves might be a candidate indicator for N uptake and accumulation at different growth stages, and activities of NR, GS, GOGAT, and endopeptidase (EP) in flag leaves at heading stage for rice yield and NMPE, NPE, NAE, NRE.