Wali Mariem, Fourati Emna, Hmaeid Nizar, Ghabriche Rim, Poschenrieder Charlotte, Abdelly Chedly, Ghnaya Tahar
Laboratoire des Plantes Extremophiles (LPE), Centre de Biotechnologies de la Technopole de Borj Cedria, BP 901, Hammam Lif, 2050, Tunisia.
Environ Sci Pollut Res Int. 2015 Jul;22(14):10769-77. doi: 10.1007/s11356-015-4298-9. Epub 2015 Mar 12.
It has previously been shown that certain halophytes can grow and produce biomass despite of the contamination of their saline biotopes with toxic metals. This suggests that these plants are able to cope with both salinity and heavy metal constraints. NaCl is well tolerated by halophytes and apparently can modulate their responses to Cd. However, the underlying mechanisms remain unclear. This study explores the impact of NaCl on growth, Cd accumulation, and Cd speciation in tissues of the halophyte Sesuvium portulacastrum. Seedlings of S. portulacastrum were exposed during 1 month to 0, 25, and 50 μM Cd combined with low salinity (LS, 0.09 mM NaCl) or high salinity (HS, 200 mM NaCl) levels. Growth parameters and total tissue Cd concentrations were determined, in leaves, stems, and root. Moreover, Cd speciation in these organs was assessed by specific extraction procedures. Results showed that, at LS, Cd induced chlorosis and necrosis and drastically reduced plant growth. However, addition of 200 mM NaCl to Cd containing medium alleviated significantly Cd toxicity symptoms and restored plant growth. NaCl reduced the concentration of Cd in the shoots; nevertheless, due to maintenance of higher biomass under HS, the quantity of accumulated Cd was not modified. NaCl modified the chemical form of Cd in the tissues by increasing the proportion of Cd bound to pectates, proteins, and chloride suggesting that this change in speciation is involved in the positive impact of NaCl on Cd tolerance. We concluded that the tolerance of S. portulacastrum to Cd was enhanced by NaCl. This effect is rather governed by the modification of the speciation of the accumulated Cd than by the reduction of Cd absorption and translocation.
先前的研究表明，某些盐生植物尽管其盐生栖息地受到有毒金属的污染，但仍能生长并产生生物量。这表明这些植物能够应对盐分和重金属的双重胁迫。盐生植物对氯化钠具有良好的耐受性，并且显然可以调节它们对镉的反应。然而，其潜在机制仍不清楚。本研究探讨了氯化钠对盐生植物海马齿组织生长、镉积累和镉形态的影响。将海马齿幼苗暴露于0、25和50 μM镉，并分别结合低盐度（LS，0.09 mM氯化钠）或高盐度（HS，200 mM氯化钠）水平，持续1个月。测定了叶片、茎和根的生长参数以及组织中镉的总浓度。此外，通过特定的提取程序评估了这些器官中镉的形态。结果表明，在低盐度条件下，镉会导致叶片黄化和坏死，并显著抑制植物生长。然而，在含镉培养基中添加200 mM氯化钠可显著减轻镉毒性症状并恢复植物生长。氯化钠降低了地上部镉的浓度；然而，由于在高盐度条件下生物量较高，镉的积累量并未改变。氯化钠通过增加与果胶酸盐、蛋白质和氯化物结合的镉的比例，改变了组织中镉的化学形态，这表明这种形态变化与氯化钠对镉耐受性的积极影响有关。我们得出结论，氯化钠增强了海马齿对镉的耐受性。这种效应主要是由积累的镉的形态变化引起的，而不是由镉吸收和转运的减少引起的。
