Heavy Metal Accumulation by the Halophyte Species Mediterranean Saltbush

Abstract

To identify Cd- and Zn-accumulating plants exhibiting a high growth rate, seeds from the halophyte species Mediterranean saltbush (Atriplex halimus L.) were collected on a heavy-metal-contaminated site in southeastern Spain (Llano del Beal, Cartagena). Seedlings from this ecotype were exposed for 3 wk to 0.1 mM Cd or Zn in a nutrient solution in a fully controlled environment. All plants remained alive and no significant growth inhibition was recorded until the end of the experiment. Mean Cd and Zn accumulation in aerial parts was 830 and 440 mg kg(-1), respectively, and the rate of metal translocation even increased with the duration of stress exposure. Resistance to heavy metals in this species may be partly linked to precipitation of Cd in oxalate crystals in the stems. A Cd-induced decrease in glutathione concentration also suggests that phytochelatins overproduction may occur in these conditions. We conclude that Mediterranean saltbush, which is able to produce up to 5 Mg dry matter ha(-1) yr(-1), may be an effective species for phytoextraction and should be tested for this purpose in field conditions.

Zinc and cadmium accumulation by Lupinus uncinatus Schldl. grown in nutrient solution

“…A similar increase in root and leaf Zn as a response to 3-week exposure to 0.1 mM Cd in nutrient solution has been reported by Lutts et al (2004) with A. halimus. Moreover, Cd and Zn appear to compete for certain organic ligands in vivo.…”

“…Fodor et al (1996) demonstrated that in cucumber (Cucumis sativus L.), a strong inhibition of photosynthesis may result from Fe deficiency in Cd-treated plants. While 10 lM Cd reduced by more than 90 % the leaf Fe concentration of Cucumber, Lutts et al (2004) found that 0.1 mM Cd had no effect at all on the leaf Fe concentration of A. halimus.…”

“…Iron concentrations of content of leaves were not affected significantly by Zn or Cd treatments (Table 4). Lutts et al (2004) reported reduced Fe concentrations in stem of saltbush (Atriplex halimus L.) in response to 0.1 mM Zn in solution culture. However, they did not note any inhibition in Fe accumulation in spite of a reduced translocation from roots to shoots.…”

NaCl protects against Cd and Cu-induced toxicity in the halophyte Atriplex halimus

“…The specific increase in Na + concentration observed in root and leaf tissues of plants simultaneously exposed to NaCl and Cu 2+ suggests that Na + could play a specific role in response to abiotic stress. Similarly, in other C4 species an increase in Na + endogenous content has been found after plant exposure to different abiotic stress conditions, this could be because Na is needed for an efficient phosphoenolpyruvate regeneration (Lutts et al, 2004). Cu 2+ and Cd 2+ induce the formation of harmful ROS, which causes irreversible damage to macromolecules such as lipid and proteins.…”

The tolerance of Atriplex halimus L. to environmental stresses

“…Experiments performed with A. halimus in pots of contaminated soil (Manousaki and Kalogerakis, 2009;Martí nezFernández and Walker, 2012;Pérez-Esteban et al, 2013), in hydroponic culture (Lefèvre et al, 2009;Lutts et al, 2004) or in Petri dishes (Márquez-Garcí a et al, 2013) show that its growth is tolerant of high concentrations of Cd, Cu, Mn, Ni, Pb or Zn in the medium. Lutts et al (2004) found that a 3-week exposure to elevated external Cd, whch produced leaf DM Cd concentrations as high as 618 μg g -1 , did not reduce shoot growth significantly, for plants of A. halimus grown from seeds of a population from a contaminated site in southern Spain. This indicates a very-high degree of tolerance, since values in excess of 5 μg g -1 are generally phytotoxic (Kabata-Pendias, 2001).…”