Shade and iron plaque of Sesbania affect cadmium accumulation in rice: A new strategy for safe production in contaminated soil

Intercropping Sesbania with rice provides a sustainable mode for the biological control of cadmium (Cd) translocation in crop grains, but how they reduce Cd accumulation in rice grain remains unclear. Here, hydroponic, pot and field assays were conducted to reveal the mechanisms of their interspecific competition for Cd assimilation, especially with regard to the effects of shade by leaves and iron plaque by roots. Results showed compared with planting rice alone, intercropping of Sesbania leading to an approximate 50% decrease in the Cd concentration of rice grain. The shade effect induced by Sesbania leaves decreased the photosynthetic and transpiration rates of rice leaves by 8.8% and 25% respectively, which is mainly occurred after the booting stage. The shade effect also markedly reduced the Cd transfer from roots to grains. Growing Sesbania decreased rhizosphere pH, stimulated the root activity of rice, strengthened iron plaque formation but enhanced Cd retention in rice roots. The batch of Fe treatments evidenced the iron plaque failed to impede Cd translocation into roots unless the value of DCB-Fe was higher than 26 mg kg-1. These results together indicated that strong scrambling for soil Cd in Sesbania roots and the shade effect in Sesbania leaves drove the reduction of Cd accumulation in rice grains. This study extends the knowledge that utilizing the intercropping plant to biologically reduce the accumulation of Cd in the crop.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).