Bioaccumulation and Physiological Response of Five Willows to Toxic Levels of Cadmium and Zinc

Abstract

We evaluated the phytoremediation potential of Salix spp. exposed to high cadmium (Cd) and zinc (Zn) concentrations to select feasible plant materials for restoration and revegetation of mining soil contaminated by heavy metals on the basis of their Cd and Zn accumulation, Cd-Zn interaction on bioaccumulation, and the changes of photosynthetic parameters. The Cd and Zn concentrations were in the order of root > leaf > stem, regardless of the species. In the combined Cd and Zn treatment, the leaf and stem Cd concentration in all species were higher relative to Cd-alone treatment. In contrast, the Zn concentration in plant tissues when exposed to the combined Cd + Zn treatment decreased relative to the Zn-alone treatment. The translocation factor (TF) of Cd and Zn from root to leaf was generally higher compared to TF from root to stem than those in the single treatment. The Cd + Zn treatments resulted in enhanced translocation of Cd from root to aboveground tissue (synergistic), while the same treatment suppressed the Zn translocation from root to leaf and stem (antagonistic). The reduction of photosynthetic parameters in Zn alone and Cd + Zn treatments was generally higher than that of Cd-alone treatment. Among the different species, S. caprea and P. alba×glandulosa have the lowest photosynthetic reduction relative to the control. Overall, S. caprea could be a potential candidate for phytoremediation of Cd- and Zn-contaminated sites.