Detrimental effect of chloride on suppressing cadmium accumulation in rice grains: A field-based investigations

Cadmium (Cd) contamination in rice ecosystems poses significant threats to global food security and ecological sustainability. This study addresses the urgent need to understand how chloride (Cl-) addition impacts on Cd dynamics in the soil-rice system, given the widespread use of Clcontaining materials in agriculture practices. Our findings indicated that Cl- addition significantly lowered soil pH, increased redox potential (Eh), and facilitated the formation of Cl-Cd complexes, enhancing Cd solubility, mobility, and bioavailability. Cl- also decreased DTPAextractable iron (Fe) and manganese (Mn), indirectly increasing Cd uptake by rice roots (by 17.4-65.0 %) through upregulation of OsNramp1 and OsNramp5 transport genes, while diminishing iron plaque formation on roots by 23.1-27.2 %. Furthermore, Cl- facilitated Cd translocation from roots to shoots via upregulation of OsHMA2 gene, leading to elevating Cd accumulation in rice tissues and increasing Cd levels in brown rice by 41.3-76.1 %. Field trials corroborated that Cl- application in slightly acidic, Cd-contaminated soils exacerbated Cd accumulation in rice grains, posing heightened risks to food safety. These results underscore the critical need to limit Cl-containing materials in agriculture to safeguard crop safety and protect ecological health.