Departmento de Ciências e Tecnologia da Biomassa, Faculdade de Ciências e Tecnologia,Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Environ Sci Pollut Res Int. 2011 Aug;19(7):2644-57. doi: 10.1007/s11356-012-0757-8.
The halophyte Halimione portulacoides collected in a polluted area of the river Sado estuary (Portugal) and obtained from hydroponic cultures was used to evaluate the compartmentation of Zn and its preferential binding sites. In parallel, we tried to assess if the minimum available Zn concentration found in marsh soil induces changes at the ultrastructural level.
A sequential extraction method was used to study the Zn compartmentation within the cell. Both dried plant samples and extracts/residues from compartmentation studies were digested by HNO3–HClO4 (4:1) until dryness and analyzed by atomic absorption spectrophotometry. Segments of young leaves, previously exposed to Zn were fixed in glutaraldehyde and osmium tetroxide. Ultrathin sections were stained and examined by transmission electron microscopy at 80 kV.
Proteins and carbohydrates of the cell walls constitute preferential binding sites of Zn, containing between 25% and 33% and between 30% and 40% of the total, respectively. Hydroponic plants accumulate Zn in their leaves up to (194 μg g−1) without visible damage or changes in the protein and chlorophyll concentrations, compared with the controls. Chlorenchyma chloroplasts of Zn-treated plants exhibited an unusual number of starch grains, which can be seen as an alert mechanism.
Although so far the levels of Zn in the leaves within the studied area have not reached high values, monitoring them remains a priority. Also, issues related with starch synthesis and organic ligands must be evaluated. The understanding of the predictable behavior of this halophyte is our main goal, and the results here presented can contribute to this achievement.
本研究从萨多河口（葡萄牙）受污染地区采集的盐生植物滨藜，并通过水培实验，来评估锌的分区情况及其优先结合位点。同时，我们试图评估在湿地土壤中发现的最低有效锌浓度是否会在超微结构水平上引起变化。
采用连续提取法研究细胞内锌的分区情况。干燥的植物样本和分区研究的提取物/残渣均用 HNO3–HClO4（4:1）消解至干燥，并用原子吸收分光光度法进行分析。先前暴露于锌的幼叶段用戊二醛和四氧化锇固定。超薄切片用醋酸双氧铀和柠檬酸铅染色，在 80 kV 下通过透射电子显微镜观察。
细胞壁的蛋白质和碳水化合物是锌的优先结合位点，分别占总量的 25%至 33%和 30%至 40%。与对照组相比，水培植物在叶片中积累的锌高达（194 μg g−1），但没有可见的损伤或蛋白质和叶绿素浓度的变化。经锌处理的植物的叶肉叶绿体显示出异常数量的淀粉粒，这可以看作是一种警报机制。
尽管到目前为止，研究区域内叶片中的锌含量尚未达到高值，但对其进行监测仍是当务之急。此外，还必须评估与淀粉合成和有机配体相关的问题。了解这种盐生植物的可预测行为是我们的主要目标，这里呈现的结果可以为此做出贡献。
