Asparagine Formation in Soybean Nodules

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Abstract
15NH4+ and [15N](amide)-glutamine externally supplied to detached nodules from soybean plants (cv. Tamanishiki) were incorporated within nodule tissues by vacuum infiltration and metabolized to various nitrogen compounds during 60 minutes of incubation time. In the case of 15NH4+ - feeding, the 15N abundance ratio was highest in the amide nitrogen of glutamine, followed by glutamate and the amide nitrogen of asparagine. In 15N content (micrograms excess 15N), the amide nitrogen of asparagine was most highly enriched after 60 minutes. 15NH4+ was also appreciably assimilated into alanine. When [15N](amide)-glutamine was fed to detached nodules, 15N was almost entirely in the amide nitrogen of asparagine. The result indicates the presence of active glutamine-linked asparagine synthesizing systems in soybean root nodules.