ZINC, LEAD AND CADMIUM TOLERANCE, UPTAKE AND ACCUMULATION BY TYPHA-LATIFOLIA

Zinc, lead and cadmium tolerance in four populations of Typha latifoli a raised from seed collected from metal-contaminated and uncontaminate d sites were investigated. Metal concentrations in natural plant popul ations showed that Zn, Pb and Cd in the leaves were maintained at low levels (Zn: 22-122, Pb: 4.7-40 and Cd: 0.2-0.8 mu g g(-1) d. wt), alth ough concentrations of these metals in the associated soil-sediments ( total concentrations of Zn: 86-3009, Pb: 26-18894 and Cd: 1.4-26 mu g g(-1) d. wt) and in the roots (Zn: 46-946, Pb: 25-3628 and Cd: 1.0-17 mu g g(-1) d. wt) varied widely. Some differences were found between m etal-contaminated and uncontaminated populations in terms of metal upt ake under controlled conditions. Seedlings from metal-contaminated pop ulations accumulated considerably more metals (up to nearly twice as m uch Zn and Pb and three times as much Cd) in roots than the uncontamin ated population in a pot trial. In general, however, different populat ions of T. latifolia showed similar growth responses (the longest leaf elongation, the longest root elongation, shoot and root d. wt), metal uptake and indices of metal tolerance when seedlings were grown in th e same metal treatment solutions or in the same metal-contaminated med ia under laboratory conditions. The data do not support the hypothesis that populations from metal-contaminated sites have evolved tolerance to Zn, Pb and Cd, but rather that T. latifolia shows constitutional t olerance.