Soybean Inoculated With One Bradyrhizobium Strain Isolated at Elevated [CO] Show an Impaired C and N Metabolism When Grown at Ambient [CO].

Soybean ( L.) future response to elevated [CO] has been shown to differ when inoculated with strains isolated at ambient or elevated [CO]. Plants, inoculated with three strains isolated at different [CO], were grown in chambers at current and elevated [CO] (400 vs. 700 ppm). Together with nodule and leaf metabolomic profile, characterization of nodule N-fixation and exchange between organs were tested through N-labeling analysis. Soybeans inoculated with SFJ14-36 strain (isolated at elevated [CO]) showed a strong metabolic imbalance, at nodule and leaf levels when grown at ambient [CO], probably due to an insufficient supply of N by nodules, as shown by N-labeling. In nodules, due to shortage of photoassimilate, C may be diverted to aspartic acid instead of malate in order to improve the efficiency of the C source sustaining N-fixation. In leaves, photorespiration and respiration were boosted at ambient [CO] in plants inoculated with this strain. Additionally, free phytol, antioxidants, and fatty acid content could be indicate induced senescence due to oxidative stress and lack of nitrogen. Therefore, plants inoculated with strain isolated at elevated [CO] may have lost their capacity to form effective symbiosis at ambient [CO] and that was translated at whole plant level through metabolic impairment.