Nickel Accumulation in the Endemic Species Odontarrhena orbelica From Pirin Mountain, Bulgaria

In the present study, we evaluated the capacity of the endemic species Odontarrhena orbelica , which occurs exclusively on non‐serpentine soils, to accumulate Ni. Initial field data on Ni accumulation are presented for O. orbelica and Odontarrhena muralis , both growing under natural conditions on non‐serpentine soils, and Odontarrhena decipiens , which grows on serpentine soil. To further assess the Ni accumulation capacity of O. orbelica in comparison with O. muralis and O. decipiens , two controlled experiments were conducted: (1) a pot experiment using different soil types—three serpentine soils, one carbonate soil, and one volcanic soil; and (2) a hydroponic experiment with increasing concentrations of NiSO 4 (10, 25, 50, 100, 500, 1000, and 3000 μM). In both the field and pot experiments, concentrations of Ni, Fe, Mn, Zn, Ca, and Mg were measured in roots, stems, and leaves using ICP‐OES. Root‐to‐leaf translocation factors and bioaccumulation factors were also calculated. In the hydroponic experiment, Ni concentrations in roots, stems, and leaves were determined, and bioaccumulation factors were also calculated. The results clearly indicate that O. orbelica behaves as a Ni excluder. In contrast, O. decipiens exhibited characteristics of a hyperaccumulator in both the pot and hydroponic experiments, showing high tolerance to increasing Ni concentrations. Odontarrhena muralis accumulated Ni in serpentine soils and demonstrated both tolerance and high bioaccumulation factors, up to approximately 2000 μM Ni. In comparison, O. orbelica showed very low tolerance to elevated Ni concentrations.