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Abstract: This work was planned for providing useful information about the possibility of using serpentine adapted plants for phytoextraction of cadmium, element scarcely represented in such metalliferous environment. To this aim, we investigated variation in cadmium tolerance, accumulation and translocation in three Alyssum plants with different phenotypes: Alyssum bertolonii, that is a serpentine endemic nickel hyperaccumulator, and two populations of Alyssum montanum, one adapted and one not adapted to serpentine soils. Plants were hydroponically cultivated in presence of increasing concentrations of CdSO4 for two weeks. For the metal concentration used in the experiments, the three different Alyssum populations showed variation in cadmium tolerance, accumulation and content. The serpentine adapted population of A. montanum showed statistically higher cadmium tolerance and accumulation than A. bertolonii and the population of A. montanum not adapted to serpentine soil thus deserving to be investigated for phytoextraction purposes. Furthermore, as for the kinetic parameters of the cadmium uptake system, A. montanum serpentine population presented a low apparent K m value, suggesting a high affinity for this metal of its uptake system, whereas the V max values were not significantly different among the plants. Present data revealed metallicolous plants are also suitable for the phytoremediation of metals underrepresented in the environment of their initial origin. Nonetheless, field trials on real contaminated soils are essential. [Copyright &y& Elsevier]

Populations of the serpentine-endemic nickel-hyperaccumulator Alyssum bertolonii from nine different outcrops were investigated for differences in their nickel tolerance and accumulation levels and shoot:root ratio of nickel concentration. Plantlets from the different populations were cultivated in hydroponics culture and subjected to a range of nickel concentrations. For populations of this obligate serpentinophyte, the results showed significant intra-specific differences in the degree of both nickel tolerance and nickel accumulation. Among populations there was no correlation between the patterns of shoot and root tolerance, whereas there was a clearly correlated pattern for root and shoot nickel accumulation. The populations of this hyperaccumulator showed a significant variation also in shoot:root ratio in nickel concentration, but there was no relationship between this trait and shoot nickel accumulation levels. Regarding the still obscure relationship between metal tolerance and hyperaccumulation, our results demonstrated a strong positive linear relationship between these two phenomena in the nickel hyperaccumulator Alyssum bertolonii. [Copyright &y& Elsevier]