选用水稻氮高效基因型IR72和9311及氮低效基因型Lemont和PECOS，采用土培方法，在5个施氮量（0、0.51、1.02、1.53、2.04 g N 钵-1,分别相当于0、75、150、225、300 kg N hm-2）处理下，研究了生理生化特性对氮肥的反应及与氮效率的关系。结果表明，在幼穗分化期，氮高效基因型水稻的可溶性蛋白含量相对低，而谷氨酰胺合成酶（GS）活性高；不同氮效率基因型间1,5-二磷酸核酮糖羧化酶/加氧酶(Rubisco)含量的差异不大；两种氮效率基因型间的净光合速率（Pn）在幼穗分化期差异不明显。而在齐穗期，氮低效基因型的Pn比高效基因型的低28.66%左右；氮低效基因型在两个时期的单位叶绿素光合速率（Pn/Chl）比氮高效基因型分别低18.51%和29.67%左右。在成熟期，氮高效基因型干物质积累能力强，籽粒产量高。这些结果说明氮效率不同的基因型对氮肥的生理反应差异大。相关性分析表明，低氮水平时(0~1.53 g N 钵-1)， GS酶活性与收获时生物量呈显著或极显著正相关；氮肥偏生产力（PFP）、氮肥农学利用率（AE）及氮素生理利用率（NUEb）分别与GS活性、Pn/Chl和齐穗期的Pn呈显著正相关，而与可溶性蛋白含量、Rubisco含量显著负相关；氮肥吸收效率（RE）与这些生理指标没有显著相关。结果表明水稻光合特征及氮代谢与水稻氮效率间存在紧密的关系，GS活性和可溶性蛋白含量对评价水稻氮肥利用率具有重要的参考价值。
Improvement in nitrogen use efficiency (NUE) in crop plants is significant in the view of economic efficiency and environment friendly. A better understanding of the physiological mechanism underlying nitrogen use efficiency is necessary for genotype screening and breeding rice cultivar with high NUE. In present study, four rice genotypes identified as high and low nitrogen use efficiency (NUE) were used to investigate their responses of physio-biochemical properties to N-fertilizer and its relationship with NUE at the rate of 0, 0.51, 1.02, 1.53, and 2.04 g N pot-1 (equivalent to 0, 75, 150, 225, 300 kg N ha-1, respectively) under pot-grown conditions. The results showed that the soluble protein content in leaves was relatively lower in high-NUE genotypes than that in low-NUE genotypes at panicle initiation stage, while the glutamine synthetase (GS) activity was higher significantly. Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) content in leaves appeared to be no significant difference between two NUE types of rice. The net photosynthetic rate (Pn) in the low-NUE genotypes was significantly lower by 28.66% in comparison with that in high-NUE genotypes at full heading stage, regardless of no significant difference at panicle initiation stage. Interestingly, Pn per chlorophyll unit (Pn/Chl) was lower in low-NUE genotypes than in high-NUE genotypes at both two stages by about 18.51% and 29.67%, respectively. Total aboveground biomass and grain yield at five nitrogen levels were significantly higher in high-NUE genotypes than those in low-NUE genotypes. It was observed GS activity was significantly correlated with biomass at harvest stage at the rate of 0, 0.5, 1.0, and 1.5 g N pot-1. Pn at full heading stage, GS activity, and Pn/Chl were all significantly and positively correlated with agronomy efficiency (AE), partial factor production of applied N (PFP), and nitrogen physiology efficiency (NUEb), respectively. However, PFP, AE, and NUEb were negatively correlated with soluble protein content in leaves, respectively. Additionally, no significant correlation was observed between nitrogen recovery efficiency (RE) and the physiological parameters mentioned above. The results presented in the paper suggest the important contributions of Pn and GS to NUE. According to the relationships among NUE, GS and soluble protein content, GS activity and soluble protein content in leaves might be candidate indicators for NUE evaluation in rice.
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