Cadmium accumulation in populations of Thlaspi caerulescens and Thlaspi goesingense

The capacity to accumulate cadmium (Cd) and zinc (Zn) was compared in Thlas pi goesingense and four populations of Thlaspi caerulescens. Two population s of T. caerulescens were grown in hydroponics at five concentrations of Cd . In addition, plants were grown in pots containing compost in which three different concentrations of Cd and two concentrations of Zn were added. A f ield trial was conducted to compare Zn and Cd uptake by three populations o f T. caerulescens on nine selected plots of the Woburn Market Garden Experi ment (UK) which had been contaminated to different degrees with heavy metal s owing to past applications of sewage sludge. Results show that the four p opulations of T. caerulescens had the same ability to hyperaccumulate Zn bu t were significantly different in terms of Cd accumulation. Two populations of T. caerulescens from Southern France accumulated much more Cd than the populations from Prayon (Belgium) and Whitesike (UK). Generally, uptake of Cd was not decreased by increased concentrations of Zn in the substrate. Th ese results indicate that the mechanisms of Cd and Zn hyperaccumulation are not identical in this species. This is the first report of hyperaccumulati on of Cd by T. goesingense, but the growth of this species was markedly red uced by the large concentrations of Zn in the substrate. Future work should focus on the differences between Cd and Zn uptake in hyperaccumulator plan ts at the species and population level.