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 g−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.