The Presence of Two Cd-Binding Components in the Roots of Water Hyacinth Cultivated in a Cd2+-Containing Medium

To find why water hyacinth accumulates the toxic heavy metalion Cd²⁺, the plant was cultivated in a mineral medium supplementedwith Cd²⁺. Cd accumulated in the roots against the concentrationgradient, mostly as a soluble form in the cytoplasm. Chromatographywith Sephadex G-25 and G-50 columns showed that the accumulatedCd was present in two forms with mol wt of 2,300 and 3,000.The components carrying Cd showed a high ratio of absorbanceat 254 nm to that at 280 nm, which suggests that they resemblemammalian Cd-thioneins. These components were not detected inthe roots of water hyacinth cultivated in the absence of Cd²⁺,indicating that they are formed in response to the Cd²⁺ supplement. (Received September 6, 1984; Accepted November 30, 1984)