Iron and copper micronutrients influences cadmium accumulation in rice grains by altering its transport and allocation

Highlights: • We examined the potential of adjusting micronutrients elements (Fe and Cu) for reducing Cd in rice grains. • Fe and, especially, Cu significantly reduced the influx of Cd ions into roots. • Cu alone significantly increased the proportion of bioavailable Cd in rice leaves. • Remediation for Cd-contaminated alkaline paddy soil with high Cu could target increasing Fe and reducing Cu concentrations. Cadmium (Cd) contamination in rice paddy fields constitutes a serious health issue in some parts of China. Here we study the potential for remediation of Cd contaminated alkaline paddy soil with low iron (Fe) and high copper (Cu) background by altering the concentrations of Fe and Cu in the growing media, which has been only seldom considered. We assessed how these two micronutrients (Cu and Fe) affect the absorption and transport of Cd in rice. Adding Cu significantly increased rice biomass and grain yield by reducing root Cd influx and Cd upward transport which, consequently, lowered Cd concentrations in roots, culms and leaves. However, excessive Cu also promoted a relatively higher Cd allocation in grains, especially under Fe deficiency, likely because Cu significantly increased the proportion of bioavailable Cd in leaves. Contrastingly, Fe did not alleviate the toxic effects of Cd on rice growth and yield, but it significantly reduced Cd transfer towards grains, which might be attributed to a sharp decrease in the proportion of bioavailable Cd in leaves. Our results demonstrated that Cd remediation may be achieved through altering Fe and Cu inputs, such that Cd accumulation in rice grains is reduced.