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田间试验说明大豆植株全生育期间固氮作用至少出现两个高峰。第一高峰较小,在营养生长开始阶段;第二高峰在开花到结荚中期。结荚后期固氮作用显著降低。固氮速率与根瘤鲜重变化趋势基本一致。溶液喷雾培养大豆幼苗的试验说明NO_3-N含量超过30ppm时,严重抑制固氮作用。NO_3-N含量愈低,单株根瘤鲜重愈高,说明其固氮能力也愈强,单株根瘤鲜重与乙炔还源之间的相关系数为+0.85。 以标记甲酸滴于出苗后23天的大豆幼苗第一复叶的中小叶上,24小时后第二复叶(未展开)及根瘤中放射性强度较高,在茎、子叶以及根中较低。分析各器官甲酸同化中间产物,在固氮作用被强烈抑制的植株中其阳性和中性离子化合物放射性强度按根、根瘤、叶片的次序递减;根瘤固氮作用受抑制的植株,其天门冬氨酸-谷氨酸代谢池增加,柠檬酸-苹果酸代谢池减少。 根据试验结果讨论了有关大豆碳氮关系以及碳素同化途径的问题。
Field experiment shows that nitrogen fixation has at least two peaks during the whole growth period of soybean plants. The first peak is smaller, at the beginning of vegetative growth; the second peak is in the midst of flowering to podding. Nitrogen fixation at the late pod stage was significantly reduced. Nitrogen fixation rate and root nodular fresh weight changes basically the same. Soybean seedling solution spray test shows that NO_3-N content of more than 30ppm, the serious inhibition of nitrogen fixation. The lower the content of NO_3-N, the higher the fresh weight of single root nodule, indicating that its nitrogen fixation ability is also stronger. The correlation coefficient between fresh root nodule weight and acetylene source is +0.85. The formic acid was dropped on the middle and small leaves of the first compound leaf of soybean seedlings 23 days after emergence. The second compound leaf (unexpanded) and the nodule 24 hours after the emergence were higher in radioactivity, and lower in stems, cotyledons and roots. The plant formate assimilation intermediates of various organs were analyzed. The radioactivity intensity of positive and neutral ionic compounds decreased in the order of roots, nodules and leaves in plants strongly inhibited by nitrogen fixation. The plant with nodulation of nitrogen fixation was inhibited and the activity of aspartate - Glutamate metabolism pool increased, citric acid - malic acid metabolism pool decreased. According to the results of the experiment, we discussed the relationship between carbon and nitrogen in soybean and the path of carbon assimilation.