Effects of Nano-Cerium Oxide on Seed Germination and Seedling Growth of Vitex negundo

Cerium oxide nanoparticles(CeO_(2) NPs)are likely to have dramatic impacts on plant performances,yet the effects of CeO_(2) NPs on seed germination and seedling growth have not been fully explored.In this study,the seed germination and seedling growth of subshrub species Vitex negundo under different concentrations of CeO_(2) NPs(low-1 mg/L,medium-100 mg/L,high-500 mg/L)have been discussed.Results showed that:(1)The seed germination rate reduces by 11.25%and 2.5%under the low and medium concentrations of CeO_(2) NPs,respectively,but increased by 7.08%under the high concentration;(2)CeO_(2) NPs had significant effects on the growth traits(root length,shoot height and biomass)of seedlings,being the highest under the medium concentration and the lowest under the highest concentration;(3)The superoxide dismutase activity was the maximum(355.91 U/g),but the protein concentration was the minimum(3.85 ug/mL)under the high concentration of CeO_(2) NPs.Our results indicated that the effects of CeO_(2) NPs on seed germination and seedling growth are concentration-dependency,i.e.,low and medium concentrations inhibited while high concentration promoted seed germination,however,seedling growth showed opposite responses.Therefore,appropriate CeO_(2) NPs concentrations are beneficial to the seed germination and seedling growth of Vitex negundo and improve the physiological performance of seedlings and enhance their adaptability to environmental adversity.