Laboratoire des Plantes Extrêmophiles, Centre de Biotechnologie de Borj-Cédria, BP 901, 2050 Hammam-lif, Tunisia.
Groupe de Recherche en Physiologie végétale (GRPV), Earth and Life Institute - Agronomy - Université catholique de Louvain, 1348 Louvain-la-Neuve, Belgium.
Ecotoxicol Environ Saf. 2016 Apr;126:122-128. doi: 10.1016/j.ecoenv.2015.12.029. Epub 2015 Dec 30.
Citrate, malate and histidine have been involved in many processes including metal tolerance and accumulation in plants. These molecules have been frequently reported to be the potential nickel chelators, which most likely facilitate metal transport through xylem. In this context, we assess here, the relationship between organics acids and histidine content and nickel accumulation in Mesembryanthemum crystallinum and Brassica juncea grown in hydroponic media added with 25, 50 and 100 µM NiCl2. Results showed that M. crystallinum is relatively more tolerant to Ni toxicity than B. juncea. For both species, xylem transport rate of Ni increased with increasing Ni supply. A positive correlation was established between nickel and citrate concentrations in the xylem sap. In the shoot of B. juncea, citric and malic acids concentrations were significantly higher than in the shoot of M. crystallinum. Also, the shoots and roots of B. juncea accumulated much more histidine. In contrast, a higher root citrate concentration was observed in M. crystallinum. These findings suggest a specific involvement of malic and citric acid in Ni translocation and accumulation in M. crystallinum and B. juncea. The high citrate and histidine accumulation especially at 100µM NiCl2, in the roots of M. crystallinum might be among the important factors associated with the tolerance of this halophyte to toxic Ni levels.
柠檬酸盐、苹果酸盐和组氨酸参与了许多过程，包括植物的金属耐受性和积累。这些分子经常被报道为潜在的镍螯合剂，很可能有助于金属通过木质部运输。在这种情况下，我们在这里评估了在添加 25、50 和 100 µM NiCl2 的水培介质中生长的马齿苋（Mesembryanthemum crystallinum）和油菜（Brassica juncea）中有机酸和组氨酸含量与镍积累之间的关系。结果表明，马齿苋对镍毒性的耐受性相对较高。对于这两个物种，木质部运输的镍含量随着镍供应的增加而增加。镍和木质部汁液中的柠檬酸浓度之间建立了正相关关系。在油菜的地上部分，柠檬酸和苹果酸的浓度明显高于马齿苋的地上部分。此外，油菜的地上部分和根部分别积累了更多的组氨酸。相比之下，在马齿苋中观察到根中柠檬酸浓度更高。这些发现表明，在马齿苋和油菜中，苹果酸和柠檬酸特别参与了镍的转运和积累。在 100µM NiCl2 下，马齿苋根中柠檬酸和组氨酸的大量积累，可能是这种盐生植物耐受有毒镍水平的重要因素之一。
