Selenium inhibits cadmium uptake and accumulation in the shoots of winte wheat by altering the transformation of chemical forms of cadmium in soil

This study aimed to investigate the effects of selenium application on cadmium absorption, transport, and soil cadmium forms of winter wheat at different stages. A pot experiment with one Cd application (6 mg·kg−1) and five Se application levels (0, 1, 2, 5, and 10 mg·kg−1) was conducted. The results showed that Se application increased the grain yield of winter wheat, especially at 5 mg·kg−1 under Cd stress. As Se was supplied at 5 (Se5) and 10 (Se10) mg·kg−1, the Cd concentrations in roots and shoots, including stems, spikes, glumes, and grains, decreased at different growth stages, and the decreases in grain were 46.1% and 70.9% respectively. Se5 and Se10 also significantly decreased the translocation factors of Cd from roots to shoots, roots to stems, stems to spikes, and glumes to grains, promoted the accumulation of Cd in roots, and inhibited the accumulation of Cd in shoots and final grains at different growth stages, and the accumulation of Cd in grains decreased by 16.9% and 68.1%, respectively. High levels of Se application (Se5 and Se10) decreased the concentrations and proportions of exchangeable Cd (EXC−Cd) and iron (Fe)−manganese (Mn) oxide−bound Cd (R2O3−Cd) but increased the concentration and proportion of residual Cd (RES−Cd) in both soils with wheat and fallow soil at different growth stages. Therefore, under Cd stress, high levels of Se application reduced the shoot Cd concentration by inhibiting the uptake and transport of Cd from roots to shoots, and decreased the bioavailability of Cd in both soil with wheat and fallow by enhancing the transformation and distribution of RES-Cd from EXC-Cd and R2O3-Cd.