Carbohydrates in Soybean Nodules

Abstract

During the first few days of nitrogen fixation activity by soybean (Glycine max (L.) Merr) root nodules, d-chiro-inositol, myo-inositol, sucrose, α,α-trehalose, and maltose accumulate rapidly and reach concentrations several fold greater than concentrations in other plant organs. Concentrations of d-pinitol in nodules (≥1.0 milligrams per gram fresh weight) were similar to concentrations in leaf blades. The concentration of fructose in nodules was lower than concentrations in other plant organs. Comparison of nonnodulated roots, nodulated roots (after removal of nodules), and nodules indicated that nodules may compete successfully with roots for carbohydrates, especially the disaccharides sucrose, α,α-trehalose, and maltose. Based on the isolation of protoplasts and bacteroids, it was tentatively concluded that the highest concentrations of cyclitols in soybean nodules are located in the infected region and that, inside infected cells, the highest concentrations of d-pinitol and myo-inositol are outside of bacteroids. Evidence for the identification of d-chiro-inositol and maltose in soybean nodules is presented.