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

Cerium oxide nanoparticles (CeO2NPs) are likely to have dramatic impacts on plant performances, yet the effects of CeO2NPs 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 CeO2NPs (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 CeO2NPs, respectively, but increased by 7.08% under the high concentration; (2) CeO2NPs 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 CeO2NPs. Our results indicated that the effects of CeO2NPs on seed germination and seedling growth are concentrationdependency, i.e., low and medium concentrations inhibited while high concentration promoted seed germination, however, seedling growth showed opposite responses. Therefore, appropriate CeO2NPs 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.