Synthesis, Antibacterial Properties, and Physiological Responses of Nano-Selenium in Barley (Hordeum vulgare L.) Seedlings Under Cadmium Stress

Selenium (Se) nanoparticles have emerged as a vital tool in enhancing plant resilience to multiple stress factors. So, the present study was designed to synthesize nano-Se, evaluate its antibacterial properties, and to investigate the effects of nano-Se at 2, 5, 10, and 15 μM on the growth and physiological responses of barley seedlings under Cd stress. The results showed that nano-Se with an average size of 24.71 nm exhibited strong antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Notably, 5 μM nano-Se reduced Cd concentrations in leaves and roots by 19.46% and 31.07%, respectively, while enhancing root length, shoot/root fresh weight (FW), and dry weight (DW) compared to Cd-stressed plants. Furthermore, exogenous nano-Se significantly increased chlorophyll, protein, amino acid content, and enhanced photosynthetic performance compared to Cd treatment alone. Nano-Se further boosted the activity of antioxidant enzymes and concurrently reduced malondialdehyde (MDA), hydrogen peroxide (H2O2), proline, total flavonoids, and total phenols levels. Moreover, nano-Se supplementation under Cd stress promoted the uptake of essential nutrient elements and increased sugar content. Our results collectively suggest that nano-Se application during Cd stress may enhance photosynthesis, promote carbohydrate metabolism, and mitigate oxidative damage, thereby improving barley growth under Cd toxicity.