Physiological Effects of MgO and ZnO Nanoparticles on the Citrus maxima

Toxicity of MgO and ZnO nanoparticles at concentrations of 250, 500 or 1 000 mg/L for Citrus maxima seedlings was investigated to evaluate the potentiality of their use as nano-fertilizers. Uptake and translocation of metal oxide nanoparticles and lipid peroxidation were measured and compared with those of plants exposed to the highest equivalent concentrations of Mg2+ and Zn2+. MgO nanoparticles were translocated from roots to shoots, while translocation of ZnO nanoparticles was low. Exposure to Mg2+ and MgO at all concentrations entailed severe toxicity and strong oxidative stress. ZnO nanoparticles showed only mild toxicity, while Zn2+ caused leaf vein chlorosis and strong oxidative stress to plant shoots. In conclusion, the toxicity of MgO nanoparticles to the plant resulted from the dissolved Mg2+ concentration, while that of ZnO nanoparticles was not correlated with the dissolved Zn2+ concentration. Our findings are significant for development and application of MgO and ZnO nanoparticles as nano-fertilizers in agriculture.