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Report No.

Real-time imaging of nitrogen fixation in an intact soybean plant with nodules using $$^{13}$$N-labeled nitrogen gas

Ishii, Satomi; Suzui, Nobuo; Ito, Sayuri; Ishioka, Noriko; Kawachi, Naoki; Otake, Norikuni*; Oyama, Takuji*; Fujimaki, Shu

Real-time images of nitrogen fixation in an intact nodule of hydroponically cultured soybean (Glycine max [L] Merr.) were obtained. In this study, we developed a rapid method to produce and purify $$^{13}$$N (half life: 9.97 min)-labeled radioactive nitrogen gas. $$^{13}$$N was produced from the $$^{16}$$O (p, $$alpha$$) $$^{13}$$N nuclear reaction. CO$$_{2}$$was filled in a target chamber and irradiated for 10 min with protons at energy of 18.3 MeV and electric current of 5 $$mu$$A which was delivered from a cyclotron. All CO$$_{2}$$ in the collected gas was absorbed and removed with powdered soda-lime in a syringe, and replaced by helium gas. The resulting gas was injected into GC and separated, and 35 mL of fraction including the peak of [$$^{13}$$N]-nitrogen gas was collected by monitoring the chromatogram. The obtained gas was mixed with 10 mL of O$$_{2}$$ and 5 mL of N$$_{2}$$ and used in the tracer experiment. The tracer gas was fed to the underground part of intact nodulated soybean plants and serial images of distribution of $$^{13}$$N were obtained noninvasively using PETIS (positron-emitting tracer imaging system). The rates of nitrogen fixation of the six test plants were estimated as 0.17 $$pm$$ 0.10 $$mu$$mol N$$_{2}$$h$$^{-1}$$ (mean $$pm$$ SD) from the PETIS image data. The decreasing rates of assimilated nitrogen were also estimated as 0.012 $$pm$$ 0.011 $$mu$$mol N$$_{2}$$h$$^{-1}$$ (mean $$pm$$ SD).



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Category:Plant Sciences



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