Accumulation of Heavy Metals in Cell Walls of Polygonum cuspidatum Roots from Metalliferous Habitats

The distribution and accumulation of Cu²⁺, Zn²⁺ and Cd²⁺ ionsin the roots of Polygonum cuspidatum, collected from metalliferousand non-metalliferous habitats, were examined. About 90% ofthe metal ions was located in the cell wall fraction of rootsof plants grown in either type of habitat. The metal-ion exchangecapacity of the cell walls is not specific to the plants frommetalliferous habitats, and there were no significant differencesamong plants from the various habitats. The capacity for Cu²⁺ions was greater than that for Zn²⁺ or Cd²⁺ ions. Cu²⁺ ionshave a high affinity for the cell wall and, thus, it appearsthat the cell wall is a barrier for the transportation of Cu²⁺into the cytoplasm. (Received March 10, 1988; Accepted March 17, 1989)