HEAVY METALS IN HYPERACUMULATOR PLANTS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。植物对重金属的吸收不仅是一个重要的基础研究领域，而且对人类营养也有影响，其应用于污染土壤的植物修复，以及从天然富金属土壤中提取金属，否则不适合传统的采矿作业。这些植物能够在其地上部分的干质量中积累百分之几的金属。这些植物的不同寻常的生理机能是世界范围内广泛研究的课题，而植物内部金属的形态形成是目前最有趣的研究课题之一。在最近的一项研究中（K¿pper et al., 2004），在表皮占组织体积最大的组织（如叶片）中，主要发现了弱氧配体。在其他组织中，很大一部分配体是强配体（硫配体为镉，组氨酸配体为锌）。计划中的项目将通过直接测量冷冻水合样品中不同功能的单个选定细胞的EXAFS来阐明组织之间的这些差异是否真的源于特定细胞类型中不同的金属形态。这一知识将揭示是否不同的组织，或在同一组织中具有不同功能的细胞，可能需要不同的重金属毒性保护策略。这种差异是假定的，但迄今为止从未进行过调查。2004年7月的初步研究指出了今后成功完成这些实验所需解决的问题和解决办法。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Heavy metal uptake in plants is not only an important basic research area, but also has an impact on human nutrition and its application for the phytoremediation of contaminated soils as well as for the commercial extraction of metals from naturally metal-rich soils otherwise unsuitable for conventional mining operations. These plants are able to accumulate several percent of metals in the dry mass of their above-ground parts. The unusual physiology of these plants is a topic of intensive worldwide research efforts, being the speciation of the metals inside the plant one of the presently most interesting research topics. In a recent study (K¿pper et al., 2004) in tissues where the epidermis comprises the largest tissue volume (e.g. leaves), mainly weak oxygen ligands were found. In other tissues, a significant proportion of the ligands were strong ligands (sulphur ligands for cadmium and histidine for zinc). The planned project shall elucidate, by directly measuring EXAFS of individual selected cells of various functions, in frozen-hydrated samples, whether these differences between tissues really originate from a different speciation of the metal in specific cell types. This knowledge would reveal if different tissues, or cells with different function in the same tissue, may need a different strategy of protection from heavy metal toxicity. Such differences have been assumed but so far were never investigated. Preliminary studies in July 2004 pointed out problems and solutions regarding the resolution needed for a future successful completion of these experiments.