Estimating Metallothionein in Small Root Samples of Agrostis gigantea and Zea mays Exposed to Cadmium

An established procedure for enrichment of Cu-binding protein was adapted to metallothionein in roots exposed to Cd. Metallothionein in Agrostis gigantea and maize was quantitated by the amount of Cd in prepurified protein fractions. Differential pulse polarography, an independent estimate of protein, was a reliable predictor of Cd content only in metallothionein fractions of Agrostis roots exposed to 3 mmol m(-3) Cd or less and not in maize. Up to 34 % of the Cd in roots of Agrostis plants was associated with metallothionein. The Cd in metallothionein of maize increased 9 fold as the root Cd content tripled during four days of exposure to 3 mmol m(-3) CdSO(4).