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

摘要

The tracer N-15(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 N-15(2)-labeled air in a 500 mL plastic cylinder. Plants fed N-15(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 N-15(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 N-15 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.