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Report No.

Quantitative analysis of the initial transport of fixed nitrogen in nodulated soybean plants using $$^{15}$$N as a tracer

Hung, N. V. P.*; Watanabe, Shiori*; Ishikawa, Shinji*; Otake, Norikuni*; Sueyoshi, Kuni*; Sato, Takashi*; Ishii, Satomi; Fujimaki, Shu; Oyama, Takuji*

The quantitative analysis of the initial transport of fixed $$^{15}$$N in intact nodulated soybean plants was investigated at the vegetative stage and pod-filling stage by the $$^{15}$$N pulse-chase experiment. The nodulated roots were exposed to N$$_{2}$$ gas labeled with a stable isotope $$^{15}$$N for 1 hour. Plant roots and shoots were separated into three sections with the same length of the main stem or primary root. Approximately 80% and 92% of fixed N was distributed in the basal part of the nodulated roots at vegetative and pod-filling stage the end of 1 hour of $$^{15}$$N$$_{2}$$ exposure, respectively. In addition, about 90% of fixed $$^{15}$$N was retained in the nodules and 10% was exported to root and shoot after 1 hour of $$^{15}$$N$$_{2}$$ exposure at pod-filling stage. The percentage distribution of $$^{15}$$N in the nodules at pod-filling stage decreased from 90% to 7% during the 7 hours of the chase-period, and increased in the roots (14%), stems (54%) leaves (12%), pods (10%), and seeds (4%). The $$^{15}$$N distribution was negligible in the distal root segment, suggesting that nitrogen fixation activity was negligible and recycling fixed N from the shoot to the roots was very low in the initially short time of the experiment.



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Category:Plant Sciences



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