Nitrogen Fixation and Translocation in Young Sugarcane (Saccharum officinarum L.) Plants Associated with Endophytic Nitrogen-Fixing Bacteria.

The tracer (15)N(2) was used to investigate sites of N(2) fixation and the possible translocation of the fixed N. Young sugarcane plants (Saccharum officinarum L.) from a stem cutting were exposed to (15)N(2)-labeled air in a 500 mL plastic cylinder. Plants fed (15)N(2) for 7 days were grown in normal air for a further chase period. After 21 days, about half of the N originating in the stem cutting had been transported to the shoot and roots, suggesting that the cutting played a role in supplying N for growth. After 3 days of feeding, the percentage of N derived from (15)N(2) was higher in the roots (2.22%) and stem cutting (0.271%) than the shoot (0.027%). Most of the fixed N was distributed in the 80% ethanol-insoluble fractions in each plant part, and the (15)N fixed either in the roots or in the stem cutting remained there and was not appreciably transported to the shoot. The results were quite different from the fate of fixed N in soybean nodules, which is rapidly transported from nodules to roots and shoots.