Mechanisms of Enhanced Rice Growth and Nitrogen Uptake by Nitrate

摘要

Rice is being increasingly cultivated in intermittently irrigated regions and also in aerobic soil in which Nitrate (NO3-)plays important role in nutrition of plant. However, there is no information regarding the influence of nitrate on the overall growth and uptake of nitrogen (N) in rice plant. Solution culture experiments were carried out to study the effects of NO3-on the plant growth, uptake of N, and uptake kinetics of NH4+ in four typical rice (Oryza sativa L.) cultivars (conventional indica, conventional japonica, hybrid indica, and hybrid japonica), and on plasma membrane potential in roots of two conventional rice cultivars (indica and japonica) at the seedling stage. The results obtained indicated that a ratio of 50/50 NH4+-N/NO3--N increased the average biomass of rice shoots and roots by 20% when compared with that of 100/0NH4+-N/NO3--N. In case of the 50/50 ratio, as compared with the 100/0 ratio, total N accumulated in shoots and roots of rice increased on an average by 42% and 57%, respectively. Conventional indica responds to NO3- more than any other cultivars that were tested. The NO3- supply increased the maximum uptake rate (Vmax) of NH4+ by rice but did not show any effect on the apparent Michaelis-Menten constant (Km) value, with the average value of Vmax for NH4+ among the four cultivars being increased by 31.5% in comparison with those in the absence of NO3-. This suggested that NO3-significantly increased the numbers of the ammonium transporters. However, the lack of effect on the Km value also suggested that the presence of NO3- had no effect on the affinity of the transporters for NH4+. The plasma membrane potential in the roots of conventional indica and japonica were greatly increased by the addition of NO3-, suggesting that NO3- could improve the uptake of N by roots of the rice plant. In conclusion, the mechanisms by which NO3- enhances the growth and N uptake of rice plant was found by the increased value of Vmax of NH4+ and increased plasma membrane potential. Thus promotion of nitrification in paddy soil is of great significance for improving the production of rice.

机译：水稻在间歇灌溉地区和需氧土壤中的种植越来越多，在这些土壤中硝酸盐（NO3-）在植物营养中起着重要作用。但是，没有关于硝酸盐对水稻植株整体生长和氮素吸收的影响的信息。进行了溶液培养实验，研究了NO3对四种典型水稻（普通ry稻，常规粳稻，杂交hybrid稻和杂交hybrid稻）植物生长，N吸收和NH4 +吸收动力学的影响。两个常规水稻品种（ind稻和粳稻）苗期根系的质膜电位。所得结果表明，与100 / 0NH4 + -N / NO3--N相比，比例为50/50 NH4 + -N / NO3--N可使稻芽和根的平均生物量增加20％。在50/50的情况下，与100/0的比率相比，水稻的芽和根中积累的总氮分别平均增加42％和57％。常规in稻对NO3-的反应比其他任何受测品种高。 NO3的供应增加了水稻对NH4 +的最大吸收速率（Vmax），但对表观Michaelis-Menten常数（Km）值没有显示任何影响，四个品种中NH4 +的Vmax平均值增加了31.5。％与没有NO 3-的那些相比。这表明NO3显着增加了铵转运蛋白的数量。但是，对Km值的影响不足也表明NO3-的存在对转运蛋白对NH4 +的亲和力没有影响。添加NO 3可大大提高常规in稻和粳稻根系的质膜电位，这表明NO 3可以提高水稻根系对氮的吸收。总之，通过增加NH4 +的Vmax值和增加质膜电位，发现了NO3-促进水稻植物生长和吸收N的机制。因此，促进稻田土壤硝化作用对提高水稻产量具有重要意义。

Mechanisms of Enhanced Rice Growth and Nitrogen Uptake by Nitrate

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