College of Life Science and Technology, Central South University of Forestry and Technology, Changsha, 410004, PR China; National Engineering Laboratory for Applied Technology of Forestry & Ecology in South China, Changsha, 410004, PR China.
College of Life Science and Technology, Central South University of Forestry and Technology, Changsha, 410004, PR China.
Chemosphere. 2019 Dec;237:124531. doi: 10.1016/j.chemosphere.2019.124531. Epub 2019 Aug 6.
Xanthium strumarium L. is a candidate species for manganese (Mn)-phyto-remediation. To reveal the mechanism of this species adaptive to Mn stress, the growth, Mn subcellular distribution, chemical forms, as well as micro-structure and ultra-structure responses of the mining ecotype (ME) of X. strumarium to Mn stress were studied with the non-mining ecotype (NME) as the reference by a hydroponic experiment. The results showed the ME demonstrated a higher tolerance to Mn stress with a superior growth and a higher tolerance index (TI) when compared with the NME. The concentrations of Mn in leaves, stems, and roots of the ME were 1.1-1.8, 1.2-1.9, and 1.3-1.9 times higher than those in the corresponding organs of the NME, respectively. The micro-structure and ultra-structure showed abnormal alterations, such as shrunken ducts and sieve canals, round-shaped chloroplasts, increased starch and osmiophilic granules, as well as expanded and non-compact granum thylakoids in the NME, compared to the ME. More than 83% of Mn was localized in cell wall and soluble fraction, while the Mn concentration in all fractions had a direct linear relationship with Mn treatment in the ME. The proportions of pectates and protein integrated-Mn, phosphate-Mn, and oxalate-Mn forms were dominant in leaves and stems of the ME, whereas, in the NME the relative proportions of inorganic Mn and water-soluble Mn forms in the roots was higher than the other forms. Altogether, the combination of preferential distribution of Mn in the cell wall and soluble fraction, and storage of Mn in low toxicity forms, such as phosphate-Mn, pectates and protein-bound Mn, and oxalate-Mn, might be responsible for alleviating Mn toxicity in the ME.
苍耳（Xanthium strumarium L.）是一种候选的锰（Mn）植物修复物种。为了揭示该物种适应 Mn 胁迫的机制，本研究采用水培实验，以非矿区生态型（NME）为对照，研究了矿区生态型（ME）苍耳在 Mn 胁迫下的生长、Mn 亚细胞分布、化学形态以及微观和超微结构的响应。结果表明，与 NME 相比，ME 对 Mn 胁迫具有更高的耐受性，表现出更好的生长和更高的耐受力指数（TI）。ME 叶片、茎和根中 Mn 的浓度分别比 NME 中相应器官中的 Mn 浓度高 1.1-1.8 倍、1.2-1.9 倍和 1.3-1.9 倍。与 ME 相比，NME 的微观和超微结构显示出异常改变，如缩小的导管和筛管、圆形叶绿体、增加的淀粉和嗜锇颗粒以及扩张和不致密的类囊体垛叠。超过 83%的 Mn 定位于细胞壁和可溶部分，而 ME 中各部分的 Mn 浓度与 Mn 处理呈直接线性关系。在 ME 的叶片和茎中，果胶和蛋白整合-Mn、磷酸盐-Mn 和草酸盐-Mn 形式的比例占主导地位，而在 NME 中，根中无机 Mn 和水溶性 Mn 形式的相对比例高于其他形式。总之，Mn 在细胞壁和可溶部分的优先分配以及 Mn 以低毒性形式（如磷酸盐-Mn、果胶和蛋白结合-Mn 和草酸盐-Mn）储存，可能有助于减轻 ME 中的 Mn 毒性。
