The effects of cerium oxide nanoparticles on reducing copper ion absorption and improving tolerance in rice under copper stress

Excessive copper in the soil is toxic to plants. Cerium oxide nanoparticles (CeO 2 NPs) can act as a nanoenzyme to enhance plant tolerance to abiotic stress. This study explored the mitigation effect of CeO 2 NPs on copper stress in rice by setting four concentration gradients (0, 50, 100, and 150 mg·L − 1 ) of CeO 2 NPs. The results showed that foliar spraying of 50 mg·L − 1 CeO 2 NPs increased total chlorophyll content, improved the antioxidant capacity and Pn (net photosynthetic rate), and promoted rice growth. Compared to CK (control), copper stress significantly increased the copper ion content in leaves by 103.05%. Under copper stress, foliar spraying with 50 mg·L − 1 CeO 2 NPs significantly decreased the copper ion content in leaves by 8.41%. The plant–pathogen interaction, plant hormone signal transduction, and sesquiterpenoid and triterpenoid biosynthesis pathways enriched by differentially expressed genes (DEGs) had the smallest P-adjust, suggesting that CeO 2 NPs may regulate the adaptability of rice to copper stress through multiple mechanisms. The analysis results of differential metabolites showed that CeO 2 NPs may act as bioactive molecules in the metabolism of flavonoids. This study is a preliminary exploration of CeO 2 NPs to alleviate copper stress in rice, and the detailed mitigation mechanism needs further study. The results of this study are conducive to promoting the health and stability of agricultural ecosystems and providing technical support for the sustainable development of agriculture.