Comparison of Biomass and Metal Uptake between Two Populations ofPhragmites australisGrown in Flooded and Dry Conditions

The biomass and metal concentrations of two populations of Phragmites australis were studied by growth in a glasshouse in three ameliorated substrata [Mai Po (MP) sediment, fly ash (FA) and lead/zinc mine tailings (TL)] under flooded and dry conditions for 90 d. Plants were raised from seeds from ‘clean’ (Mai Po, Hong Kong) and metal-contaminated (Plombières, Belgium) sites. Seedling growth was best in fly ash, root dry weights being higher in flooded than dry conditions, and growth poorest in tailings, in which shoot and root dry weights were higher under dry conditions for both populations. However, in the MP substratum conditions did not significantly affect shoot and root dry weights of either population. In the fly ash and tailings, more metals were generally taken up in both roots and shoots in flooded than dry conditions, but there was little difference in the MP substratum. Metal uptake was mostly similar in both populations in seedlings grown in the same substratum, there being no clear evidence of ecotypic differentiation.