Nickel Tolerance and Accumulation Capacities in Different Populations of the Hyperaccumulator Noccaea caerulescens

Abstract: A comparative analysis of nickel (Ni) accumulation by the hyperaccumulator Noccaea japonica (H. Boissieu) F.K. Mey originating from ultramafic (serpentine) soil and plants from 16 populations of the hyperaccumulator Noccaea caerulescens F.K. Mey originating from ultramafic (serpentine), calamine and non-metalliferous soils, was performed. The plants were grown for 2 weeks in half-strength Hoagland’s solution without Ni, followed by a 6-week exposure to NiSO₄ at a non-toxic concentration (1 μM). The Ni concentration in the roots and shoots was determined by atomic absorption spectrophotometry. In N. japonica, the Ni concentration in the shoots was significantly lower than in the roots, and lower than that in the shoots of N. caerulescens from the ultramafic populations. The ability of plants from different populations of N. caerulescens to accumulate Ni in roots (per unit dry weight) decreased in the following order: Puente Basadre ≈ Le Coulet > St-Baudille ≈ Cira ≈ Prémanon > Viviez ≈ Monte Prinzera > Les Avinières > Moravskoslezké > Le Bleymard ≈ Krušné Hory ≈ Wilwerwiltz ≈ La Calamine ≈ St-Félix-de-Palliéres ≈ Kuopio > Prayon. The value of the translocation factor in N. japonica did not significantly differ from that in the ultramafic population Puente Basadre of N. caerulescens, whereas it varied within wide limits among the N. caerulescens populations. The highest Ni translocation factor was obtained for the population Monte Prinzera from the ultramafic group and the populations Krušné Hory and Kuopio from the non-metallicolous group, whereas the lowest values were obtained for the calamine populations La Calamine and Prayon. In N. caerulescens, the Ni concentration in the roots was uncorrelated with the Ni concentration in the shoots, but significantly positively correlated with Ni tolerance. The high Ni tolerance in ultramafic populations is apparently explained by a high capacity to sequester Ni in the roots themselves, and not directly related to the root-to-shoot translocation capacity.