Heavy metal translocation and accumulation in iron plaques and plant tissues for 32 hybrid rice (Oryza sativa L.) cultivars

Rice (Oryza sativa L.) planted on heavy metal contaminated soil is a source of toxic elements entering the food chain and thereby posing a threat to human health. The main objective of this study was to investigate heavy metals uptake, translocation, and accumulation differences in iron plaque and rice tissues among the rice cultivars. In the present study, 32 hybrid rice cultivars were cultured on heavy metal contaminated paddy soil. Pb, Cd, Cu, and Zn concentrations in rice tissues (root, straw, husk, and brown rice) and in the iron plaques on rice root surfaces were measured. Significant differences of Pb, Cd, Cu, and Zn tolerance, concentrations and accumulation in 32 rice cultivars were observed. However, no significant difference was observed in concentrations of Pb, Cd, Cu, and Zn in two-line hybrid rice and three-line hybrid rice. The concentrations of Pb in iron plaques were significantly positive linearly correlated with concentrations of Pb in rice roots, and concentrations of Cd and Cu were significantly negative linearly correlated with Cd and Cu in rice roots. The concentrations of heavy metal in brown rice were significantly positively correlated with the translocation factors TFhb (from husk to brown rice) and TFsh (from straw to husk). It indicated that iron plaque plays an important role in mediating heavy metal entering into rice roots, and heavy metal accumulation in brown rice was related to its ability to transfer in the husk and straw rather than the root.