低pH影响大豆和菜豆对氮素形态的响应

通过室内水培试验，模拟了植株生长的缺氮、纯铵、纯硝3个不同氮素营养环境，研究了两种豆科作物（大豆和菜豆）幼苗生长对氮素及氮素形态的响应，同时对溶液pH进行了实时监测；在单一供铵的基础上，研究了在不同pH（pH 4.5，pH 6.5）下两种豆科作物对铵态氮的响应特征，并利用实时定量PCR技术，探究了植株体内的铵转运蛋白（AMT）基因对pH的响应规律；通过构建系统进化树、关键位点序列比对，对不同物种的AMT蛋白进行了生物信息学分析。研究结果表明：与缺氮处理相比，纯硝处理显著增加了大豆和菜豆的生物量，尤其是根系生物量，而纯铵处理下无显著变化；但是纯铵与纯硝处理下植株体内的氮积累量基本相同，且发现纯铵处理下溶液pH显著下降。通过控制纯铵处理的溶液pH，我们发现相比于pH 6.5，pH 4.5显著降低了两种豆科作物的生物量。进一步研究了大豆体内的主要铵转运蛋白基因的表达情况，结果显示相比于pH 6.5，pH 4.5显著降低了大多数铵转运蛋白基因的表达量；生物信息学分析表明，大豆和菜豆的AMT在亲缘关系上高度相近，而与喜铵作物水稻的亲缘关系较远。本研究表明大豆和菜豆对铵态氮的吸收会导致根际环境酸化，从而限制植株生长，这为田间提高豆科作物的氮素营养提供了一个视角。

Effects of Low pH on Response of Legume Crops to Nitrogen Forms

To study the response of two leguminous crops to nitrogen forms, the hydroponic culture experiments with the same strength of ammonium or nitrate as sole nitrogen nutrient was conducted, and the change of pH in solution was monitored in these seven days. Based on supplying only ammonium, the response characteristics of ammonium of two legume crops under different pH (pH 4.5, pH 6.5) treatments have been studied. The expression of ammonium transporter (AMT) genes was analyzed by RT-PCR under different pH treatments. By constructing a phylogenetic tree, sequence alignment of key sites, the bioinformatics analysis of AMT proteins in different species was carried out. The results showed that, compared with nitrogen deficiency treatment, nitrate treatment significantly increased the biomass of soybean and common bean, especially root biomass, but there was no significant change under ammonium treatment. However, the total nitrogen accumulation was the same accumulated in plants under ammonium and nitrate treatment. The pH of the solution decreased significantly under ammonium treatment. By controlling the pH of the solution treated with ammonium, we found that the biomass of the two legumes was significantly reduced at pH 4.5, compared with that at pH 6.5. Results showed that the expression of most ammonium transporter genes was significantly reduced at pH 4.5, compared with pH 6.5. Bioinformatics analysis showed that the AMT of soybean and common bean was closer than that of rice. This study showed that the absorption and utilization efficiency of ammonium nitrogen by leguminous crops inhibit at lower pH, which provided a perspective for improving nitrogen nutrition of leguminous crops in the field.