Molecular Mechanisms of Salt Tolerance in Spinach Induced by Seed Priming with Surface-Modified Cerium

Surface modification is a key strategy for improving the functionality and application potential of nanomaterials. Although cerium oxide nanoparticles (CeO2 NPs) have demonstrated potential in alleviating salt stress in crops, the mechanism by which surface modifications enhance salt tolerance remains inadequately understood. This study explores how CA- and Chi-modified CeO2 NPs regulate spinach growth, physiological responses, and molecular mechanisms. The results indicated that modified CeO2 NPs significantly increased the fresh weight of spinach under salt stress and reduced malondialdehyde (MDA) content, thereby effectively mitigating membrane lipid peroxidation. Modified CeO2 NPs boosted chlorophyll content and photosynthetic rate by upregulating photosystem genes (PsbS, Lhca4, Lhcb3) and enhancing SOD, CAT, and POD activities. Notably, treatment with Chi-CeO2 NPs significantly upregulated the expression of photosynthetic genes in roots and increased the K+/Na+ ratio by approximately 11.33%, while reducing the accumulation of Na+ and Cl-. Transcriptome analysis showed that modified CeO2 NPs priming altered the expression of photosynthesis-, peroxisome-, and ion transport-related genes (e.g., HKT6, AKT1) in spinach roots and leaves under salt stress. This study clarifies how modified CeO2 NPs improve spinach salt tolerance through multi-pathway synergy, offering a theoretical and technical basis for salt-tolerant crop cultivation.