Nodule Nitrate Reductase as a Source of Reduced Nitrogen in Soybean, Glycine max

Abstract Hydroponically grown soybeans were fed 15N‐enriched NaNO3 at nine reproductive stages of development. The stem exudates contained excess 15N in the fully reduced nitrogen fraction. The soybean nodules had high nitrate reductase activity, whereas the roots had no detectable nitrate reductase activity. Based on these results, we concluded that the nodule nitrate reductase system has the potential of contributing significantly to the nitrogen economy of the plant.