ZnO nanoparticles-induced oxidative stress in Chenopodium murale L, Zn uptake, and accumulation under hydroponic culture.

To understand toxic effect of Zn oxide nanoparticles (ZnO NPs) on Chenopodium murale, 40-day-old plants were exposed to 10, 50, and 250 mg L^-1 of NPs using hydroponic system under controlled light and temperature conditions. Aboveground parts and roots were harvested 3 and 6 days after treatments and evaluated for some growth and biochemical indices. By increasing the concentration of ZnO NPs, the content of Zn increased in the roots more than the shoots. Our findings showed that all ZnO NPs treatments resulted in a decrease in growth, total chlorophyll content and soluble proteins, while the content of carotenoids, lipid peroxidation, leaf hydrogen peroxide (H₂O₂), and leaf electrolyte leakage increased significantly compared with the control. These changes, along with increased proline content and catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) activities in the treated plants, suggest that all concentrations of ZnO NPs used in this study strongly induced oxidative stress. A decline in growth-related indicators can be considered as an indicator of ZnO NPs phytoxicity in C. murale. Based on the concentration of Zn dissolved in the solution, the effects of Zn released into the nutrient solution may be greatly involved in induction of toxicity and retardation of growth at least under our experimental conditions. The results of this study suggest that an important mechanism of ZnO NPs phytotoxicity may be the exacerbation of oxidative stress and damage to biomembranes.