Nano silicon dioxide reduces cadmium uptake, regulates nutritional homeostasis and antioxidative enzyme system in barley seedlings (Hordeum vulgare L.) under cadmium stress

Cadmium (Cd) toxicity is one of the most severe environmental threats inhibiting crop growth and productivity. Strategies to mitigate the adverse effects of Cd stress on plants are under scrutiny. Nano silicon dioxide (nSiO(2)) is an emerging material and could protect plants against abiotic stress. Can nSiO(2) alleviate Cd toxicity in barley, and the possible mechanisms are poorly understood. A hydroponic experiment was conducted to study the mitigation effects of nSiO(2) on Cd toxicity in barley seedlings. The results showed that the application of nSiO(2) (5, 10, 20, and 40 mg/L) increased barley plant growth and chlorophyll and protein content, improving photosynthesis, compared with Cd-treated alone. Specifically, 5-40 mg/L nSiO(2) addition increased net photosynthetic rate (Pn) by 17.1, 38.0, 30.3, and - 9.7%, respectively, relative to the Cd treatment alone. Furthermore, exogenous nSiO(2) reduced Cd concentration and balanced mineral nutrient uptake. The application of 5-40 mg/L nSiO(2) decreased Cd concentration in barley leaves by 17.5, 25.4, 16.7, and 5.8%, respectively, relative to the Cd treatment alone. Moreover, exogenous nSiO(2) lowered malondialdehyde (MDA) content by 13.6-35.0% in roots, and by 13.5-27.2% in leaves, respectively, compared with Cd-treated alone. Besides, nSiO(2) altered antioxidant enzyme activities and alleviated detrimental effects on Cd-treated plants, attaining maximal values at 10 mg/L nSiO(2). These findings revealed that exogenous nSiO(2) application may be a viable option for addressing Cd toxicity of barley plants.