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 Cl-containing 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 DTPA-extractable iron (Fe) and manganese (Mn), indirectly increasing Cd uptake by rice roots (by 17.4% to 65.0%) through upregulation of OsNramp1 and OsNramp5 transport genes, while diminishing iron plaque formation on roots by 23.1% to 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% to 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. • Cl - increased Cd bioavailability in paddy soil, raising concerns for food safety. • Cl - educed iron plaques formation on rice roots, altering the barrier to Cd uptake. • Cl - promoted Cd transporter gene expression, influencing Cd accumulation in rice. • Cl - enhanced Cd uptake and translocation, posing risks for crop contamination. • Managing Cl - levels was essential to mitigate Cd contamination in rice production.