A Non-invasive visualizing technique for observing the symbiotic nitrogen fixation using N

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

The positron-emitting tracer imaging system (PETIS) is one of the non-invasive imaging tools for living organisms. PETIS is specialized for plant nutrition with very compact detection heads which can be installed in a growth chamber. We have been developing the total methods of PETIS, including production of various positron-emitting radiotracers such as Cd, and many studies in plant nutrition have been done using PETIS in this decade. Here, we employed N for the study of symbiotic nitrogen fixation and successfully developed a rapid method to produce and purify N-labeled nitrogen gas. The gaseous tracer was fed as a mixture of N, O and He (10:20:70) to the underground part of intact nodulated soybean plants. As a result, serial images of distribution of the fixed N were obtained, and the fixation rates were estimated 0.170.10 mol N h plant (mean SD, n=6) from the data.