Summary• Isatis capadocica, a brassica collected from Iranian arsenic-contaminated mine spoils and control populations, was examined to determine arsenate tolerance, metabolism and accumulation.• I. cappadocica exhibited arsenate hypertolerance in both mine and nonmine populations, actively growing at concentrations of > 1 mM arsenate in hydroponic solution.• I. cappadocica had an ability to accumulate high concentrations of arsenic in its shoots, in excess of 100 mg kg −1 DW, with a shoot : root transfer ratio of > 1. The ability to accumulate arsenic was exhibited in both hydroponics and contaminated soils.• Tolerance in this species was not achieved through suppression of high-affinity phosphate/arsenate root transport, in contrast to other monocotyledons and dicotyledons. A high percentage (> 50%) of arsenic in the tissues was phytochelatin complexed; however, it is argued that this is a constitutive, rather than an adaptive, mechanism of tolerance.

Summary• The divalent cations of several transition metal elements have similar chemical properties and, when present in excess, one metal can interfere with the homeostasis of another. To better understand the role of interactions between transition metals in the development of metal toxicity symptoms in plants, the effects of exposure to excess nickel (Ni) on copper (Cu) and iron (Fe) homeostasis in the Ni hyperaccumulator plant Alyssum inflatum were examined.• Alyssum inflatum was hypertolerant to Ni, but not to Cu. Exposure to elevated subtoxic Ni concentrations increased Cu sensitivity, associated with enhanced Cu accumulation and enhanced root surface Cu(II)-specific reductase activity.• Exposure to elevated Ni concentrations resulted in an inhibition of root-to-shoot translocation of Fe and concentration-dependent progressive Fe accumulation in root pericycle, endodermis and cortex cells of the differentiation zone. Shoot Fe concentrations, chlorophyll concentrations and Fe-dependent antioxidant enzyme activities were decreased in Ni-exposed plants when compared with unexposed controls. Foliar Fe spraying or increased Fe supply to roots ameliorated the chlorosis observed under exposure to high Ni concentrations.• These results suggest that Ni interferes with Cu regulation and that the disruption of root-to-shoot Fe translocation is a major cause of nickel toxicity symptoms in A. inflatum.

To assess the potential for arsenic (As) hyperaccumulation of native plant species, plant and soil samples were collected from the Zarshuran area (north-western Iran), which has a history of As pollution from mining. Total and water-soluble As in the soil ranged from 11.2 to 6525 and from 0.004 to 13.08 mg kg(-1), respectively. Among 89 plant species, the highest foliar As concentrations were found in Isatis capadocica (up to 3000 mg kg(-1)) and Hesperis persica (up to 1500 mg kg(-1)). Over a broad range of soil As concentrations, these species maintained more than 10-fold increased foliar As concentrations and soil to leaf As transfer coefficients in comparison with all the other species sampled at the same sites. Based on these characteristics, in combination with their ability to accumulate As to concentrations exceeding 1000 mg kg(-1) on a dry weight basis in their foliage, both species should be classified as As hyperaccumulators. I. capadocica and H. persica, both Brassicacaeae, are the first terrestrial angiosperms shown to possess the As hyperaccumulation trait. Both species are fairly robust with relatively high biomass productivity and, therefore, potentially useful in on site phytoremediation, particularly I. capadocica, because of its higher robustness and As accumulation capacity.

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Serpentine soils, which contain relatively high concentrations of nickel and some other metals, are the preferred substrate for some plants, especially those that accumulate Ni in their tissues. In temperate regions more Ni-hyperaccumulator plants are found in Alyssum than in any other genus. In this study, serpentine soils of two areas (Marivan and Dizaj) in the west/northwest of Iran and also perennial Alyssum plants growing on these soils were analyzed for Ni and some other metals. The highest concentrations of total metals in the soils of these areas for Ni, Cr, Co and Mn were 1,350, 265, 94 and 1,150 g g ¡1