Selenium increases photosynthetic pigments, antioxidant metabolism, flavonoid biosynthesis, nodulation, and development of soybean plants (Glycine max L.)

Purpose: This study aimed to investigate the physiological roles of Se in the photosynthetic pigment profile, oxidative metabolism, flavonoid biosynthesis, nodulation, and its role in soybean production. Methods Two independent experiments were carried out: one conducted in soil and the other in a nutrient solution. When the plants reached the V 2 growth stage, five (0, 7.5, 15, 30, and 45 µg kg − 1 ) and four Se (0, 5, 10, and 15 µmol L − 1 ) rates from a sodium selenate source were applied to soil and hydroponics-based experiments, respectively. Results The concentration of photosynthetic pigments, the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase), and the concentration of total sugars in soybean leaves increased in response to Se fertilization. In addition, Se improves nitrogen assimilation efficiency by increasing nitrate reductase activity, resulting in higher ureides, amino acids, and proteins concentration. Se increases the synthesis of daidzein and genistein in the root, resulting in a greater number of nodules and concentration and transport of ureides to the leaves. Se-treated plants showed greater growth and biomass accumulation in roots. Conclusion This research is the first report on the influence of Se on nodulation and flavonoid synthesis in leguminous plants. In the scenario of climate change and the increase of abiotic stresses in agriculture, our results contribute to increasing knowledge about the effects of Se on physiology, biochemistry, and biological nitrogen fixation in legume plants.