Selenium reduces cadmium accumulation in seed by increasing cadmium retention in root of oilseed rape (Brassica napus L.).

Graphical abstract Root is the first part directly in contact with Se and Cd in growth medium. Polysaccharides (such as hemicellulose and pectin) are critical components of cell wall, and they could bind Cd ions and limit the transport of Cd through cytomembrane. After getting through root cell walls, Se affects the subcellular distribution and chemical forms of Cd in root, which is related to the Cd translocation from root to shoot. The cell wall binding capacity and the production of Cd complexes with low mobility might be in connection with reducing Cd concentration in root and further in seed of rape. Highlights • Cd concentration in rapeseed was reduced by exogenous Se application. • Se increased the Cd concentration in root cell wall of rape. • Se improved the contents of pectin and hemicellulose 2 in root cell wall of rape. • Se increased the proportion of Cd with low movability within rape root. Abstract Cadmium (Cd) accumulation in edible part of crop threatens human health. The beneficial effects of selenium (Se) have been established in improving plant growth and reducing Cd accumulation in plant under Cd stress. This study investigated the effect of Se in reducing Cd concentration in seed, and revealed the underlying regulating mechanisms in root of rape. Results showed that when plants were grown in Cd contaminated soil, the application of exogenous Se significantly reduced Cd concentration in seed. Under 5 μmol L−1 Cd stress, the photosynthesis and photosynthetic pigment contents in leaf tissue were improved with the addition of Se; Se reduced Cd concentration in root, while root morphology showed little variation by comparison with Cd treated alone. Further studies on root revealed that Se addition increased the concentration of Cd with inactive forms. Except that, Se increased the contents of pectin and hemicellulose 2, which was consistent with the elevated Cd concentration in root cell walls. Findings in this study may indicate that with the application of Se, the proportion of less mobile Cd-complex is enhanced, and the Cd binding to root cell wall increases along with the elevated contents of pectin and hemicellulose 2; all of these contribute to the reduction of Cd uptake in root and therefore transportation to stem, pod, and finally seed. [ABSTRACT FROM AUTHOR]