Calcium-Associated Anions Play a Dual Role in Modulating Cadmium Uptake and Translocation in Wheat

Cadmium accumulation in wheat as a daily food, even in low concentrations, is a serious threat to human health. Previous studies have reported conflicting results on the impact of calcium treatments on cadmium uptake and translocation in plants due to the complex soil conditions. Our hydroponic study offers clearer insights into how specific calcium treatment parameters influence cadmium uptake and translocation in wheat. The hydroponic medium was contaminated by cadmium (CdCl2) and the following treatments were applied: CaCO3, CaSO4, CaCl2, CaCO3 + CaSO4, CaCO3 + CaCl2, and CaSO4 + CaCl2. After harvesting, the wheat was analyzed for Cd2+ uptake characteristics including translocation factor, bioconcentration factor, and uptake. Furthermore, physiological growth parameters and plant nutrients were also determined. Applying CaCO3 significantly decreased wheat Cd2+ concentration by about three times in CaCO3 and two times in CaCO3 + CaSO4 and CaCO3 + CaCl2 treatments than in Cd-control. This study clearly elucidates that pH and CO32− were crucial in reducing Cd2+ concentration in wheat. SO42−, Cl−, and Ca2+ showed no effect on Cd2+ concentration. Ca2+ only reduced the translocation factor (TF) of Cd2+ in plants. CaCO3 also declined cadmium interference in the Mg2+, Mn2+, and Cu2+ uptake. Therefore, this study provides novel insight into the pure effects of calcium treatments on controlling cadmium contamination in plants, independent of soil effect.