NiO(s) (bunsenite) is not available to Alyssum species

To determine if the Ni-hyperaccumulator Alyssum corsicum can absorb Ni from the kinetically inert crystalline mineral NiO(s) (bunsenite). A. corsicum and A. montanum plants were grown for 30 days in a serpentine Hoagland solution. NiO was provided at 0 or 0.1 g L^-1 (1.34 mmol L^-1) as reagent grade NiO particles <1 μm diameter, continuously mixed by aeration. A. corsicum and A. montanum shoots contained 19.4 and 5.2 mg Ni kg^-1 DW with NiO, and 3.0 and 1.1 mg Ni kg^-1 DW shoots, respectively in the control treatment. A. corsicum normally absorbs over 12,000 mg Ni kg ^-1 shoots when supplied 300 μM soluble Ni. Roots were coated with the NiO particles and contained 3-5% Ni at harvest. Despite the small Ni accumulation in the NiO treatment above control, A. corsicum is not capable of dissolving and hyperaccumulating Ni from NiO.