Nutrient Reabsorption Mechanism Adapted to Low Phosphorus in Wild and Cultivated Soybean Varieties

Phosphorus (P) plays an important role in soybean growth and reproduction. Wild soybean (Glycine soja) expressed higher tolerance to P-limited environment compared to cultivated soybeans (Glycine max). In this study, wild and cultivated soybean were used to compare the changes and differences in young and old leaves by ion contents and the kinds, number, and metabolic pathways of small molecule metabolites analysis under low P conditions. Our results showed that under low P conditions, Mg2+, Fe3+, and SO42- increased in young and old leaves of wild soybean; NO3- increased in young leaves of wild soybean and decreased in old leaves; H2PO4- was relatively stable in young leaves of wild soybean. And then, tricarboxylic acid (TCA) metabolism was enhanced and hexose-phosphate metabolism was inhibited in young and old leaves of wild soybean; aspartic acid family amino acids, glutamic acid family amino acids, serine family amino acids, aromatic amino acids metabolisms in young and old leaves of wild soybean were enhanced which contributed to the reuse of amino acids; disaccharides metabolism in young leaves of wild soybean was enhanced. Our experiment indicated that wild soybean could tolerate low P by promoting ion, disaccharides and amino acid metabolites accumulation and reuse in young and old leaves, and enhancing the energy metabolism in young and old leaves, and promoting the decomposition of hexose-phosphate in old leaves for reuse in young leaves. Our results provided a new insight for the cultivation of new soybean varieties with tolerance to P deficiency.