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Symbiotic nitrogen fixation in intact soybean plants is visualized non-invasively using the positron-emitting tracer imaging system (PETIS).
-A first step to enhance food production-

Mar. 17, 2009


Japan Atomic Energy Agency (JAEA) and Niigata University developed a new non-invasive method to observe symbiotic nitrogen fixation by nodules of intact soybean plants using the positron-emitting tracer imaging system (PETIS) and successfully obtained the first images that nodules absorb nitrogen gas from the air.

Symbiotic nitrogen fixation is a biological process in which leguminous plants and rhizobia collaborate to utilize nitrogen gas in the air as nutrition, and plays a key role to supply nitrogen nutrients to the crop fields in the world.
JAEA previously developed PETIS, a planar-type positron imaging system specially designed for the plant researches, which can obtain a serial image of the movement of radioactive tracer labeled with a positron-emitting nuclide in an intact plant body. In this study, a new method to produce and purify nitrogen gas labeled with 13N (half life: 9.97 min) and to feed the tracer gas to the test plants was developed. Using these techniques, the absorption of 13N-labeled nitrogen gas into the nodules on the roots of intact soybean plants was imaged, and the rates of nitrogen fixation were estimated from the image data.
The advantage of this method is the noninvasiveness. In other words, with one individual plant, multiple environmental conditions can be tested for the effects on the nitrogen fixation after an hour of waiting time for the sufficient decay of 13N. Therefore, this method may become a very effective tool for improving agricultural techniques including fertilizer management for soybean cultivation.

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