Manganese-Induced Alleviation of Cadmium Stress in Rice Seedlings

Cadmium (Cd) contamination in agricultural soils poses a significant risk to crop production and food safety. This study explored the role and mechanisms of manganese (Mn) in mitigating Cd toxicity using two rice genotypes: ZS97B (Cd-tolerant) and MY46 (Cd-sensitive). A hydroponic experiment was conducted under two Mn levels (0 and 100 µM) and three Cd levels (0, 5, 10 µM). Exposure to 10 µM Cd significantly inhibited plant growth and induced physiological disorders, with more severe effects observed in MY46 than in ZS97B. The addition of Mn markedly alleviated Cd toxicity, as reflected by increased antioxidant enzyme activities and reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents in both roots and shoots. Gene expression analysis showed that Mn addition up-regulated genes related to antioxidant enzymes and down-regulated key Cd uptake and transport genes, including OsNramp1, OsYSL2, OsMTP9, and OsHMA3. These changes contributed to enhanced antioxidant capacity and reduced Cd accumulation in rice plants under Cd stress. Our findings demonstrate that appropriate Mn application can effectively reduce Cd accumulation and alleviate toxicity in rice grown in Cd-contaminated environments.