Lanthanum supplementation at the heading stage efficiently reduces cadmium content in rice by regulating key genes involved in cadmium uptake, translocation, and redistribution pathways

Lanthanum (La) can enhance crop growth while mitigating cadmium (Cd) accumulation in the edible parts of plants. This study determined the optimal timing of La application‒specifically at the rice heading stage‒to maximize yield and suppress Cd accumulation in grains. In pot experiments, La application at the heading stage increased the grain weight by 24.6 % and reduced Cd content in grains by 60.5 %. La treatment at this stage enhanced the transfer index (TF_IN2-N1) of Cd by 29.95 % and reduced TF_N1-IN1 by 29.86 %. Low-dose La in hydroponics further inhibited Cd accumulation while supporting growth. Additionally, La treatment significantly reduced Cd levels in root cell sap and xylem sap and downregulated the expression of critical Cd transporter genes, including OsNramp5, OsNramp1, OsIRT1, and OsHMA2 in the roots and OsZIP7 in the nodes. These results reveal that La application at the heading stage minimizes Cd accumulation in rice grains by limiting Cd uptake, translocation, and redistribution through targeted gene downregulation, establishing this stage as key for maximizing yield and ensuring safer rice production.