Within and between population variation for zinc and nickel accumulation in two species of Thlaspi (Brassicaceae)

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Abstract
In this study, the differences in zinc (Zn) and nickel (Ni) hyperaccumulation were investigated between three populations of Thlaspi pindicum together with genetic variation within populations of T. pindicum and Thlaspi alpinum var. sylvium, both serpentine endemics. Three experiments were conducted under standard conditions in hydroponic assay. Each experiment contained three treatments of metal: 100 microm Zn, 100 microm Ni, and combined 100/100 microm Zn/Ni. Genetic variation within populations was determined using maternal families. No genetic variation within populations was found for either Zn or Ni hyperaccumulation for both T. pindicum and T. alpinum var. sylvium, but differences were observed for both Zn and Ni hyperaccumulation between populations of T. pindicum. In combined Zn/Ni treatments, Zn inhibited Ni translocation in both species, which is unexpected considering that these species are serpentine endemics and well known Ni hyperaccumulators. The lack of genetic variation for metal hyperaccumulation is possibly due to inbreeding. Since Zn hyperaccumulation is not manifested in the field, inadvertent uptake of Zn is a plausible hypothesis for its preferential uptake.