不同氮效率水稻生育后期氮代谢酶活性的变化特征

以不同氮效率水稻基因型为供试材料,研究了两个供氮水平下水稻生育后期功能叶和茎秆的氮、可溶性蛋白浓度和氮转运量以及氮代谢关键酶的变化。结果表明:与对照相比,施氮处理能显著增加不同氮效率水稻功能叶和茎秆的氮、可溶性蛋白的浓度和氮转运量。在不同的施氮水平下,水稻从齐穗至成熟顶三叶的氮浓度降低了60%～67%;而茎秆氮在生育后期对籽粒氮的贡献取决于环境供氮水平,与对照相比施氮处理水稻从茎秆转运出的氮大幅提高,在不同的供氮水平下南光的叶片和茎秆氮转运量显著高于Elio。与对照相比,施氮处理增加齐穗期时硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)和谷氨酸脱氢酶(GDH)的活性。随生育期的推进,四种氮代谢酶活性随之降低。南光的NR和GS酶活性显著高于Elio,但NR活性受水稻生育期和环境供氮水平的影响较大;南光的GOGAT和GDH的活性显著低于Elio。相关分析表明,NR和GS活性与功能叶和茎秆的氮转运量呈显著正相关。这就意味着水稻生育后期功能叶和茎秆的NR和GS活性高,尤其是GS活性高是筛选水稻氮高效的重要指标。

Variation of activity of N metabolizing enzymes in rice plants different in N use efficiency at their late growth stages

In rice the period of grain filling is characterized by transition of all vegetative organs from sink to source. A pot experiment was conducted to monitor variation of N and protein concentrations, N translocation and enzyme activities representative of nitrogen metabolism after the heading stage in different leaves and stem sections of two rice cultivars different in N use efficiency (NUE), high and low, treated with two levels of N fertilization. Compared with CK or Treatment N0, N application increased N concentration, soluble protein concentration and N translocation in leaves and stems. Nitrogen concentration in functional leaves decreased by 60-67% from heading to maturity, regardless of N rates, which indicates that N in grains comes mainly from leaves. However, N contribution rate from stems to grain depends on environmental N supply. N and soluble protein concentration and N translocation in leaves and stems was lower in Nanguang than in Elio at the maturity stage. Compared with CK, N application increased the activities of four N enzymes. And the activities decreased with the plant growth. The NR and GS activities were higher in Nanguang than in Elio, while NR activity depends more on N rate and growth stage. The GOGAT and GDH activities were lower in Nanguang than in Elio. NR and GS activities were significantly correlated to N and soluble protein concentrations at the heading stage and 2 weeks after the heading. All these indicate that higher NR and GS activities especially the latter, may predict the N status of rice, high N translocation and high NUE in rice.