Chromium and nickel tolerance of Trema orientalis [Blume] L. in tissue culture

Callus of Trema orientalis derived from both contaminated and uncontaminated sources were tested in vitro for their relative tolerance to chromium and nickel. The calluses derived from contaminated source were metal-tolerant and showed better growth than those obtained from uncontaminated plants. The specificity of metal tolerance shown by the parent material was maintained in the calluses. Compared to the uncontaminated explants, the calli derived from contaminated sources exhibited higher catalase and peroxidase activities but a reduced acid phosphatase activity. Biochemical studies, provided evidence that the contaminated sources were physiologically distinct from the uncontaminated ones. Thus, this study indicated that seeds of Trema orientalis collected from contaminated sites were tolerant to chromium and nickel, and may have the advantage of being used in sustainable revegetation programmes on chromiferous minewastes.