Transport of fixed nitrogen from soybean nodules inoculated with H₂-uptake positive and negative Rhizobium japonicum strains

The composition and the flow rate of xylem exudate were compared among 4 Rhizobium japonicum strains-H₂-uptake positive and negative strains. The apparent rate of nitrogen transport from the nodulated roots formed with H₂-uptake positive strains was bigher than that with Ha-uptake negative strains. Besides, the relative amount of asparagine-N in the xylem sap from the nodulated roots inoculated with H₂-uptake positive strains was higher than that with H₂-uptake negative strains though allantoin and allantoic acid were the principal forms of nitrogen in the xylem sap. It is suggested that the hydrogenase system affects the amount of fixed-N and the balance of carbon utilization in nodules and that a part of nitrogen assimilation system in the nodules may be altered.