Zinc, lead and cadmium tolerance, uptake and accumulation by Typha latifolia

Zinc, lead and cadmium tolerance in four populations of Typha latifolia raised from seed collected from metal-contaminated and uncontaminated sites were investigated. Metal concentrations in natural plant populations 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 μg g^-1 d. wt), although concentrations of these metals in the associated soil-sediments (total concentrations of Zn: 86-3009, Pb: 26-18894 and Cd: 1.4-26 μg^-1 d. wt) and in the roots (Zn: 46-946, Pb: 25-3628 and Cd: 1.0-17 μg g^-1 d. wt) varied widely. Some differences were found between metal-contaminated and uncontaminated populations in terms of metal uptake under controlled conditions. Seedlings from metal-contaminated populations accumulated considerably more metals (up to nearly twice as much Zn and Pb and three times as much Cd) in roots than the uncontaminated population in a pot trial. In general, however, different populations 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 the same metal treatment solutions or in the same metal-contaminated media 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 tolerance.