ZINC, LEAD AND CADMIUM TOLERANCE, UPTAKE AND ACCUMULATION BY THE COMMON REED, PHRAGMITES-AUSTRALIS (CAV) TRIN EX STEUDEL

Zinc (Zn), lead (Pb) and cadmium (Cd) tolerance in populations of seed lings of Phragmites australis raised from seeds collected from a mine site (Plombieres, Belgium) contaminated with Zn, Pb and Cd and three ' clean' sites (Felixstowe, UK; Wisbech, UK; and Mai Po, Hong Kong) were studied under glasshouse conditions. Small differences were found bet ween the metal-contaminated population and the three 'clean' populatio ns when seedlings were grown in 1.0 mu g ml(-1) Zn and 10.0 mu g ml(-1 ) Pb treatment solutions. In general, however, different populations o f seedlings showed similar growth responses, metal uptake and indices of Zn, Pb and Cd tolerance when cultured in the same metal-contaminate d media for 89 d or in the same metal treatment solutions (ZnSO4:1.0 a nd 4.0 mu g ml(-1) Zn; Pb(NO3)(2):10.0 and 25.0 mu g ml(-1) Pb; CdSO4: 0.5 and 1.0 mu g ml(-1) Cd) for 3 weeks. There was insufficient eviden ce to support the hypothesis that the metal-contaminated population ha s evolved to a Zn-, Pb- or Cd-tolerant ecotype but the results indicat ed some differentiation between the populations with that from Hong Ko ng being the least productive under the experimental conditions used. The implications of the findings on selection of provenances for use i n constructed wetlands for wastewater treatment are discussed. (C) 199 7 Annals of Botany Company.