Department of Animal, Plant and Soil Sciences, Centre for AgriBioscience, La Trobe University, Bundoora, Victoria, Australia.
School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland, Australia.
Ann Bot. 2019 Jan 1;123(1):121-132. doi: 10.1093/aob/mcy148.
Salt has been shown to affect Cd translocation and accumulation in plants but the associated mechanisms are unclear. This study examined the effects of salt type and concentration on Cd uptake, translocation and accumulation in Carpobrotus rossii.
Plants were grown in nutrient solution with the same Cd concentration or Cd2+ activity in the presence of 25 mm NaNO3, 12.5 mm Na2SO4 or 25 mm NaCl for ≤10 d. Plant growth and Cd uptake were measured and the accumulation of peptides and organic acids, and Cd speciation in plant tissues were analysed.
Salt addition decreased shoot Cd accumulation by >50 % due to decreased root-to-shoot translocation, irrespective of salt type. Synchrotron-based X-ray absorption spectroscopy revealed that, after 10 d, 61-94 % Cd was bound to S-containing ligands (Cd-S) in both roots and shoots, but its speciation was not affected by salt. In contrast, Cd in the xylem sap was present either as free Cd2+ or complexes with carboxyl groups (Cd-OH). When plants were exposed to Cd for ≤24 h, 70 % of the Cd in the roots was present as Cd-OH rather than Cd-S. However, NaCl addition decreased the proportion of Cd-OH in the roots within 24 h by forming Cd-Cl complexes and increasing the proportion of Cd-S. This increase in Cd-S complexes by salt was not due to changes in glutathione and phytochelatin synthesis.
Salt addition decreased shoot Cd accumulation by decreasing Cd root-to-shoot translocation due to the rapid formation of Cd-S complexes (low mobility) within the root, without changing the concentrations of glutathione and phytochelatins.
盐已被证明会影响植物中 Cd 的迁移和积累，但相关机制尚不清楚。本研究探讨了盐的类型和浓度对滨海地雀舌草（Carpobrotus rossii）中 Cd 吸收、迁移和积累的影响。
在含有相同 Cd 浓度或 Cd2+ 活度的营养液中，将植物分别培养在 25mm NaNO3、12.5mm Na2SO4 或 25mm NaCl 中≤10 天。测量植物的生长和 Cd 吸收情况，并分析植物组织中肽和有机酸的积累以及 Cd 的形态。
盐的添加使 Cd 在地上部分的积累减少了>50%，这是由于根到地上部分的转运减少，而与盐的类型无关。基于同步加速器的 X 射线吸收光谱表明，培养 10 天后，61-94%的 Cd 与根系和地上部的含硫配体（Cd-S）结合，但盐对其形态没有影响。相反，木质部汁液中的 Cd 以游离的 Cd2+或与羧基结合的形式存在（Cd-OH）。当植物暴露在 Cd 中≤24 小时时，根系中 70%的 Cd 以 Cd-OH 而非 Cd-S 的形式存在。然而，NaCl 的添加在 24 小时内通过形成 Cd-Cl 配合物和增加 Cd-S 的比例，降低了根系中 Cd-OH 的比例。盐增加 Cd-S 配合物不是由于谷胱甘肽和植物螯合肽合成的变化。
盐的添加通过减少 Cd 从根部向地上部分的转运，降低了地上部分的 Cd 积累，这是由于在根部迅速形成 Cd-S 配合物（迁移率低），而谷胱甘肽和植物螯合肽的浓度没有变化。
