Nano-silicon alters antioxidant activities of soybean seedlings under salt toxicity

Materials with a particle size less than 100 nm are classified as nano-materials. The physical and chemical properties of nano-materials can vary considerably from those of bulk materials of the same composition. Silicon (Si) still fails to get recognized as an essential nutrient for plant growth and development, however the beneficial effects in terms of growth, biotic and abiotic stress resistance have been indicated in a variety of plant species for their growth. The aim of this study was to investigate the effects of different nano-silicon rates on the growth and antioxidant activities of soybean (Glycine max L. cv. M7) under salt stress. The results showed that salinity decreased shoot and root dry weight, potassium (K⁺) concentration in the root and leaf; however, increased sodium (Na⁺) concentration, catalase, peroxidase, ascorbate peroxidase and superoxide dismutase activities, phenolic components, ascorbic acid and α-tocopherol contents, lipid peroxidation, hydrogen peroxide, and oxygen radical's concentration. Between the treatments, 0.5 and 1 mM of nanosilicon oxide (nano-SiO₂) improved shoot and root growth of seedlings. In contrast, a foliar application of SiO₂ at 2 mM reduced the soybean growth. Overall, exogenous nano-silicon alleviated the salt stress by increase in K⁺ concentration, antioxidant activities, non-enzymatic compounds and decreasing of Na⁺ concentration, lipid peroxidation, and reactive oxygen species production.