Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
Beijing Engineering Research Center for Biofuels, Tsinghua University, Beijing, 100084, China.
Environ Sci Pollut Res Int. 2016 Sep;23(18):18823-31. doi: 10.1007/s11356-016-7083-5. Epub 2016 Jun 18.
Cadmium (Cd) contamination is a worldwide environmental problem, and remediation of Cd pollution is of great significance for food production as well as human health. Here, the responses of sweet sorghum cv. 'M-81E' to cadmium stress were studied for its potential as an energy plant in restoring soils contaminated by cadmium. In hydroponic experiments, the biomass of 'M-81E' showed no obvious change under 10 μM cadmium treatment. Cadmium concentration was the highest in roots of seedlings as well as mature plants, but in agricultural practice, the valuable and harvested parts of sweet sorghum are shoots, so promoting the translocation of cadmium to shoots is of great importance in order to improve its phytoremediation capacity. Further histochemical assays with dithizone staining revealed that cadmium was mainly concentrated in the stele of roots and scattered in intercellular space of caulicles. Moreover, the correlation analysis showed that Cd had a negative relationship with iron (Fe), zinc (Zn), and manganese (Mn) in caulicles and leaves and a positive relationship with Fe in roots. These results implied that cadmium might compete with Fe, Zn, and Mn for the transport binding sites and further prevent their translocation to shoots. In addition, transmission electron microscopic observations showed that under 100 μM cadmium treatment, the structure of chloroplast was impaired and the cell wall of vascular bundle cells in leaves and xylem and phloem cells in roots turned thicker compared to control. In summary, morphophysiological characteristic analysis demonstrated sweet sorghum can absorb cadmium and the growth is not negatively affected by mild level cadmium stress; thus, it is a promising material for the phytoremediation of cadmium-contaminated soils considering its economic benefit. This study also points out potential strategies to improve the phytoremediation capacity of sweet sorghum through genetic modification of transporters and cell wall components.
镉（Cd）污染是一个全球性的环境问题，修复镉污染对于粮食生产和人类健康都具有重要意义。本研究以甜高粱品种‘M-81E’为材料，探讨其作为能源作物修复镉污染土壤的潜力。在水培实验中，10 μM 镉处理下‘M-81E’的生物量没有明显变化。幼苗和成熟植株的根中镉浓度最高，但在农业实践中，甜高粱有价值且可收获的部分是茎秆，因此促进镉向茎秆转移对于提高其植物修复能力非常重要。进一步用二硫腙染色的组织化学分析表明，镉主要集中在根的中柱，散布在幼茎的细胞间隙中。此外，相关性分析表明，镉与幼茎和叶片中的铁（Fe）、锌（Zn）和锰（Mn）呈负相关，与根中的 Fe 呈正相关。这些结果表明，镉可能与 Fe、Zn 和 Mn 竞争运输结合位点，从而阻止它们向茎秆转移。此外，透射电子显微镜观察表明，在 100 μM 镉处理下，叶片中的叶绿体结构受损，叶脉和根中的木质部和韧皮部细胞的细胞壁变厚。综上所述，形态生理特性分析表明，甜高粱可以吸收镉，在轻度镉胁迫下生长不受负面影响；因此，考虑到其经济效益，它是一种很有前途的镉污染土壤植物修复材料。本研究还指出了通过对转运蛋白和细胞壁成分进行遗传修饰来提高甜高粱植物修复能力的潜在策略。
