Site of natural N enrichment of soybean nodules.

Soybean (Glycine max L. Merrill) nodules are usually more enriched in (15)N than other tissues. We show that both bacteroids and nodule cortex are considerably more enriched in (15)N than nodule cytosol, with bacteroids being slightly more enriched than the cortex. Hence, (15)N enrichment occurs in cells of both plant and bacterial origin.