Chelated forms of trace elements improve antioxidant properties and nodulation potential of soybean-Bradyrhizobium symbiosis under insufficient water conditions

Abstract

The development of new nanotechnological approaches and the appearance of preparations with low concentrations of microelements can serve as a basis for promising solutions aimed at increasing stress-protective properties and tolerance to the adverse factors effects. The aim of the study is to show the effectiveness of seed inoculation with nodule bacteria modified by chelate forms of trace elements germanium, ferrum and molybdenum to stimulate antioxidant properties and improve the functioning of the Glycine max (L.) Merr. – Bradyrhizobium symbiosis in insufficient water supply conditions. For this, the symbiotic systems of soybean with active virulent Bradyrhizobium japonicum B1-20 were used with the addition of chelated forms of ferrum, germanium and molybdenum in a dilution of 1:1000 to the culture medium. The chelator was citric acid. At the phenological stages during active nitrogen fixation by soybeans, two models of plant watering regimes were created  ̶ optimal at the level of 60% of the full field capacity and insufficient/water stress at the level of 30% of the full field capacity. Microbiological, physiological, and biochemical methods of plant testing were used. It was found that the addition of rhizobia, chelated forms of germanium or ferrum to the culture medium, induces an increase in the antioxidant properties of plants by activating the key enzymatic complexes of superoxide dismutase and ascorbate peroxidase in soybean nodules and leaves under water stress. The use of chelated forms of ferrum or germanium led to the stimulation of the Bradyrhizobium nodulation potential, which was accompanied by the optimization of the water status and growth processes of soybean plants in insufficient moisture supply conditions. It was shown that inoculation with rhizobia containing chelated forms of molybdenum induced soybean plants sensitive to water deficit, as evidenced by an unstable reaction of enzyme activity, decrease or increase, in nodules and leaves. It inhibits nodulation processes on soybean roots and at the same time disrupts the water status of plants with insufficient water supply. It was concluded that the addition of chelated forms of germanium or ferrum to the rhizobia culture medium is a promising solution for stimulating the protective antioxidant properties of soybeans, which helps to optimize the physiological state of plants under insufficient water conditions.