Hyperaccumulation of nickel by Alyssum corsicum is related to solubility of Ni mineral species

Past studies have demonstrated that hyperaccumulators absorb Ni from the same labile pools in soil as normal plant species. This study investigated whether the Ni hyperaccumulator plant Alyssum corsicum possesses distinct extraction mechanisms for different Ni species present in soils. Different Ni species have different solubilities and potential bioavailabilities to roots. Uptake of Ni in shoots of A. corsicum was analyzed after four weeks of plant growth in nutrient solution with 17 different Ni compounds or soils. The results indicate that Ni uptake is related to Ni solubility and plant transpiration rate. The most soluble compounds had the highest Ni uptake, with the exception of Ni-3(PO4)(2), Ni phyllosilicate, Ni-acid birnessite which showed a low solubility but a relatively high plant uptake and transpiration rate. In serpentine soils and insoluble NiO plant transpiration rate was high but uptake was very low and statistically comparable to the control. It appears that Ni uptake is driven by convection, which depends on the initial concentration of Ni in solution and the plant transpiration rate.