Relationship between the nitrogen fixation and carbohydrate contents in soybean

Soybean plants fix gaseous nitrogen at the expense of carbohydrate transported from tops. In order to elucidate the physiological role of the individual carbohydrate, the time course changes of each quantity and quality were studied in relation to the nitrogen fixation activity. (+)-Pinitol, D-chiro-inositol, glucose, fructose, myo-inositol and sucrose were detected in nodules with gas-liquid chromatography. The concentration of (+)-pinitol and D-chiro-inositol decreased at the same time when the increase of nodules' weight per plant was suspended. Stems and roots contained (+)-pinitol, glucose, fructose, sucrose and a trace of myo-inositol and D-chiro-inositol. In sterns (+)-pinitol occurred as much as sucrose. (+)-Pinitol and sucrose were major carbohydrates in stems. Starch concentration in nodules paralleled with that of total sugar in roots.