Physiological and biochemical responses of soybean seedlings (Glycine max L.) to α-tocopherol treatment under salt stress

Background. Salinity is one of the most important factors affecting the growth and productivity of plants. It creates stressful conditions for legumes at the initial phases of ontogenesis. The prospects of exogenous α-tocopherol usage to increase the salt resistance of Glycine max L. were studied. The aim of the work was to study the influence of salt stress and α-tocopherol on the growth of soybean and indicators characteri­zing the antioxidant system functioning. Materials and methods. Soybean seedlings of the Oksana variety were the objects of our study. Seeds of the control group were soaked in distilled water, seeds of the experimental groups – in α-Toc acetic solutions in concentrations (0.01; 0.1; 0.5; 1.0 g/L). A 100 mM sodium chloride solution was used to create salinity. The samples of cotyledons, hypocotyls and primary roots of 10-day-old soybean were used for determination of biochemical parameters. Germination of seeds, raw weight, length of soybean hypocotyls and roots, content of TBA-reactive substances, carbonyl groups of oxidatively modified proteins, proline, catalase and ascorbate peroxidase activity were determined. Results. It was established that salinity caused inhibition of soybean seed germination and growth. Pretreatment of soybean seeds with α-Toc (0.1 and 0.5 g/L) effectively increased germination and improved growth indicators of soybean. An increase in TBA-reactive substances and oxidatively modified proteins in hypocotyls and roots of salt-stressed plants was recorded. α-Toc reduced the level of peroxidation and oxidatively modified proteins of soybean seedlings under salinity. Proline synthesis increased during the development of the salt stress reaction, and its accumulation is an adaptive response of soybean plants. The pretreatment of α-Toc caused a significant increase of proline and stimulated catalase and ascorbate peroxidase activity in soybean seedling tissues under salt stress. However, a high concentration of α-Toc (1.0 g/L) slowed down the activity of antioxidant enzymes. Conclusions. Our study suggests the participation of α-Toc in the formation of legumes salt resistance. The α-Toc pretreatment of soybean seeds improved germination and enhanced growth processes, normalized the oxidative state of the salt-stressed soybean seedlings by inhibiting peroxidation and reducing the degree of oxidatively modified proteins, stimulating the activity of antioxidant enzymes, and increasing the content of proline.