Differential roles of manganese and zinc on cadmium accumulation in rice: Mechanisms involving transport, antioxidant responses, and gene regulation

) amendments. Results showed that although soil-available Cd content was unaffected, both treatments differentially reduced Cd concentrations in plant tissues. Mn and Zn application reduced grain Cd by 26.46-33.11% and 43.67-52.60%, respectively. Notably, Mn strongly inhibited the root-to-shoot transport of Cd, reducing the translocation factor by up to 56.46% and 47.30% in the two genotypes. Conversely, a low dose of Zn increased this transport by 1.54- to 1.76-fold. Correlation analyses indicated that Zn levels in soil and rice tissues were negatively associated with root Cd, whereas Mn levels were negatively correlated with shoot Cd. Both amendments alleviated root oxidative stress and enhanced antioxidant enzyme activity. Furthermore, they differentially regulated the expression of key genes involved in Cd transport. This study demonstrates that while both Mn and Zn mitigate Cd accumulation, their dominant mechanisms differ: Zn primarily reduces Cd entry and enhances its retention in roots, while Mn predominantly restricts its upward movement to shoots. These insights provide a scientific foundation for developing tailored micronutrient management strategies to improve rice safety in Cd-contaminated environments.