Sarret Géraldine, Saumitou-Laprade Pierre, Bert Valérie, Proux Olivier, Hazemann Jean-Louis, Traverse Agnès, Marcus Matthew A, Manceau Alain
Environmental Geochemistry Group, Laboratoire de Géophysique Interne et Toctnophysique, University of Genoble and Centre National de la Recherche Scientifique, Grenoble cedex, France.
Plant Physiol. 2002 Dec;130(4):1815-26. doi: 10.1104/pp.007799.
The chemical forms of zinc (Zn) in the Zn-tolerant and hyperaccumulator Arabidopsis halleri and in the non-tolerant and nonaccumulator Arabidopsis lyrata subsp. petraea were determined at the molecular level by combining chemical analyses, extended x-ray absorption spectroscopy (EXAFS), synchrotron-based x-ray microfluorescence, and muEXAFS. Plants were grown in hydroponics with various Zn concentrations, and A. halleri specimens growing naturally in a contaminated site were also collected. Zn speciation in A. halleri was independent of the origin of the plants (contaminated or non-contaminated) and Zn exposure. In aerial parts, Zn was predominantly octahedrally coordinated and complexed to malate. A secondary organic species was identified in the bases of the trichomes, which contained elevated Zn concentrations, and in which Zn was tetrahedrally coordinated and complexed to carboxyl and/or hydroxyl functional groups. This species was detected thanks to the good resolution and sensitivity of synchrotron-based x-ray microfluorescence and muEXAFS. In the roots of A. halleri grown in hydroponics, Zn phosphate was the only species detected, and is believed to result from chemical precipitation on the root surface. In the roots of A. halleri grown on the contaminated soil, Zn was distributed in Zn malate, Zn citrate, and Zn phosphate. Zn phosphate was present in both the roots and aerial part of A. lyrata subsp. petraea. This study illustrates the complementarity of bulk and spatially resolved techniques, allowing the identification of: (a) the predominant chemical forms of the metal, and (b) the minor forms present in particular cells, both types of information being essential for a better understanding of the bioaccumulation processes.
通过结合化学分析、扩展X射线吸收精细结构光谱（EXAFS）、基于同步加速器的X射线微荧光和μEXAFS，在分子水平上测定了耐锌且超积累的拟南芥和不耐锌且非积累的琴叶拟南芥亚种中锌（Zn）的化学形态。将植物种植在含有不同锌浓度的水培溶液中，还采集了在污染场地自然生长的拟南芥标本。拟南芥中的锌形态与植物来源（污染或未污染）和锌暴露无关。在地上部分，锌主要以八面体配位并与苹果酸络合。在表皮毛基部鉴定出一种次要的有机物种，其锌浓度升高，其中锌以四面体配位并与羧基和/或羟基官能团络合。由于基于同步加速器的X射线微荧光和μEXAFS具有良好的分辨率和灵敏度，因此检测到了该物种。在水培条件下生长的拟南芥根中，仅检测到磷酸锌，据信这是由于在根表面发生化学沉淀所致。在污染土壤中生长的拟南芥根中，锌分布在苹果酸锌、柠檬酸锌和磷酸锌中。磷酸锌存在于琴叶拟南芥亚种的根和地上部分。这项研究说明了整体技术和空间分辨技术的互补性，从而能够鉴定：（a）金属的主要化学形态，以及（b）特定细胞中存在的次要形态，这两类信息对于更好地理解生物积累过程都至关重要。
