Intra-specific differences in nickel tolerance and accumulation in the Ni-hyperaccumulator Alyssum bertolonii

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.