Evaluation of the Ni2+ Phytoextraction Potential in Mesembryanthemum crystallinum (Halophyte) and Brassica juncea

Abstract

Among heavy metal stressors, nickel (Ni) pollution is one threatening risk to the environment. In this view,the growing concerns about environmental pollution have stimulated the efforts to promote the individuation of phytoextractor plants that are able to tolerate and accumulate toxic metals, including Ni, in the aerial parts. More recently, it has been suggested that halophytes, i.e. native salt-tolerant species, could be more suitable for metal extraction, from saline soils than glycophytes, most frequently used so far. In the framework of this approach, we evaluated here the Ni-phytoextraction ability of the halophyte Mesembryanthemum crystallinum comparatively to the, model species Brassica juncea. Plants were maintained for 3 months on a soil containing 0, 25, 50, and 100 ppm NiCl2. Nickel impaired the growth activity of both species. Interestingly, M. crystallinum was less impacted by NiCl2 addition. The plant mineral nutrition was differently affected by NiCl2 exposure depending on the ion, the species and even the organ. In both species, roots were the preferential sites of Ni2+ accumulation, but the fraction translocated to shoots was higher in M. crystallinum than in B. juncea. The relatively good tolerance of M. crystallinum to Ni suggests that this halophyte is more efficient to extract Ni2+ than B. juncea.