Deciphering Cd stabilization pathways by organosilicon in soil-pakchoi systems through isotope-tracing

Cadmium (Cd) pollution in farmland soils threatens food safety, making it essential to study soil-crop Cd transport mechanisms and develop remediation strategies. While organosilicon-modified materials demonstrate potential in blocking metal uptake by crops, their underlying mechanisms remain underexplored. This study employed stable isotope ¹¹⁴Cd tracing to investigate Cd absorption, translocation, allocation in soil-pakchoi system mediated by organosilicon (DMDCS and D6). Results revealed that organosilicon induced Cd redistribution in soils, enhancing its sequestration into non-reactive fractions. Specifically, DTPA-Cd decreased by 13.14-24.19 %, while RES-Cd increased by 70.3-106.8 %. Organosilicon also inhibited Cd uptake and translocation in pakchoi, reducing root and shoot Cd concentrations by 30.0-33.2 % and 54.6-57.1 %, respectively, with a 35 % decline in translocation factor (TF). This reduction stemmed from diminished Cd accumulation (12.09-17.73 % decrease) in soluble subcellular fractions. Among the plant parts, Cd isotopes were markedly fractionated: shoots were isotopically heavier than roots. Silicone application attenuated this fractionation intensity, with Δ^114/110Cd_shoot-root decreased from 0.33 to 0.08. We suggest that organosilicon suppressed the enrichment of exogenous isotopes in plant edible parts due to a 28.1 % decrease in Cd isotope exchangeability (E-value) and vacuolar compartmentalization. This study provides new insights into organosilica-mediated Cd dynamics in pakchoi, laying the foundation for future Cd regulation strategies.