Localization and chemical forms of cadmium in plant samples by combining analytical electron microscopy and X-ray spectromicroscopy

By M. Isaure, B. Fayard, G. Sarret, S. Pairis, J. Bourguignon. 2006

181 citations recorded by the source corpus.

Cadmium (Cd) is a metal of high toxicity for plants. Resolving its distribution and speciation in plants is essential for understanding the mechanisms involved in Cd tolerance, trafficking and accumulation. The model plant Arabidopsis thaliana was exposed to cadmium under controlled conditions. Elemental distributions in the roots and in the leaves were determined using scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX), and synchrotron-based micro X-ray fluorescence (μ-XRF), which offers a better sensitivity. The chemical form(s) of cadmium was investigated using Cd LIII-edge (3538 eV) micro X-ray absorption near edge structure (μ-XANES) spectroscopy. Plant μ-XANES spectra were fitted by linear combination of Cd reference spectra. Biological sample preparation and conditioning is a critical point because of possible artifacts. In this work we compared freeze-dried samples analyzed at ambient temperature and frozen hydrated samples analyzed at −170 °C. Our results suggest that in the roots Cd is localized in vascular bundles, and coordinated to S ligands. In the leaves, trichomes (epidermal hairs) represent the main compartment of Cd accumulation. In these specialized cells, μ-XANES results show that the majority of Cd is bound to O/N ligands likely provided by the cell wall, and a minor fraction could be bound to S-containing ligands. No significant difference in Cd speciation was observed between freeze-dried and frozen hydrated samples. This work illustrates the interest and the sensitivity of Cd LIII-edge XANES spectroscopy, which is applied here for the first time to plant samples. Combining μ-XRF and Cd LIII-edge μ-XANES spectroscopy offers promising tools to study Cd storage and trafficking mechanisms in plants and other biological samples.

Subfields: Analytical Chemistry, Plant Science, Pollution

View Paper: https://www.semanticscholar.org/paper/4d71dba8b5824d6e72eb627912e07bf897142b2e

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In Analytical Chemistry

P. White

In Plant Science

Citations in the corpus

Root responses to cadmium in the rhizosphere: a review. (2011, background): “…in the substrate (Wó jcik and Tukiendorf, 2004, 2005; Wu et al., 2005; Van Belleghem et al., 2007), the phytoavailability of Cd (Wó jcik and Tukiendorf, 2004; Abe et al., 2008), and the duration of exposure to Cd (Vázquez et al., 1992; Wó jcik and Tukiendorf, 2004; Isaure et al., 2006).”
Glutathione Is a Key Player in Metal-Induced Oxidative Stress Defenses (2012, background): “Other studies support that glandular trichomes can accumulate and even excrete large amounts of metals and might be considered the major compartment of Cd accumulation in leaves [174,175].”
Localization and Chemical Speciation of Cadmium in the Roots of Barley and Lettuce (2014, methodology): “Synchrotron radiation-based analytical techniques have also been used to detect Cd at the cellular and subcellular levels (Isaure et al., 2006; Naftel et al., 2007; Fukuda et al., 2008; Harada et al., 2010; Terada et al., 2010).”