The interaction between selenium (Se) species and cadmium (Cd) in soil-rice systems remains poorly understood. This study investigated the roles of selenocysteine (SeCys) and selenomethionine (SeMet) in Cd dynamics within soils and rice grains from relatively high-Se (RHSe) and relatively low-Se (RLSe) areas in Zhejiang Province, China. Structural equation modeling revealed a strong Se-Cd interaction in the soil. In the RHSe area, SeCys and SeMet formed complexes with Cd, significantly reducing their bioconcentration factor in the rice ( p < 0.05). Rice grains from the RLSe area contained only SeCys-Cd, while both SeCys-Cd and SeMet-Cd were present in the RHSe area. These variations were linked to differences in Se species composition and their binding affinities to Cd. SeCys exhibited a stronger Cd-binding capacity than SeMet due to its structural and physiological features. This study underscores the distinct roles of Se species in modulating Cd accumulation and suggests the potential of SeCys to enhance Se biofortification while mitigating Cd uptake in rice. • High soil selenium (Se) levels inhibit the bioaccumulation of cadmium (Cd) in rice. • SeCys and SeMet in high-Se soils can bind with Cd, reducing its mobility. • SeCys and SeMet in rice grains have different binding capacities for Cd. • SeCys has a stronger Cd binding affinity than SeMet in rice grains.
Niu et al. (Fri,) studied this question.