Environmental and Experimental Botany 69 (2010) 24–31 Contents lists available at ScienceDirect Environmental and Experimental Botany journal homepage: www.elsevier.com/locate/envexpbot Mapping of nickel in root cross-sections of the hyperaccumulator plant Berkheya coddii using laser ablation ICP-MS Ahmad B. Moradi a,∗ , Siegfried Swoboda b , Brett Robinson a , Thomas Prohaska b , Anders Kaestner c , Sascha E. Oswald d , Walter W. Wenzel e , Rainer Schulin a a Soil Protection group, Institute of Terrestrial Ecosystems, Dept. of Environmental Science, ETH Zürich, Switzerland b Dept. of Chemistry, University Natural Resources & Applied Life Science, Vienna, Austria c Paul Scherrer Institute, Villigen, Switzerland d Helmholtz Centre for Environmental Research -UFZ, Leipzig, Germany e Dept. of Forest & Soil Science, University Natural Resources & Applied Life Science, Vienna, Austria article info Article history: Received 7 August 2009 Received in revised form 19 January 2010 Accepted 4 February 2010 Keywords: Berkheya coddii Cortex Dimethylglyoxime Laser ablation Nickel Root cross-section Stele abstract Quantitative studies of the distribution pattern of metals in plant tissues provide important information on the potential of metal-accumulator plants for remediation and amelioration of contaminated soils. We used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) as well as staining with dimethylglyoxime (DMG) to investigate the distribution pattern of nickel (Ni) in root cross-sections of the Ni-hyperaccumulator plant Berkheya coddii Rossler. Plants were grown in rhizoboxes containing soil with 125 mg kg −1 Ni. Roots were embedded in resin and cut into sections for LA-ICP-MS analysis. For DMG- staining analysis, fresh root cross-sections were prepared using a microtome. LA-ICP-MS revealed higher Ni concentrations in the cortex (374 ± 66 mg kg −1 ) than in the stele (210 ± 48 mg kg −1 ) of the investigated roots. The distribution pattern agreed well with those found by DMG-staining. Higher concentrations of Ni were found in the stele compared to the cortex of roots of the control plants not exposed to elevated soil Ni using both techniques. Our results indicate that an active uptake or ion selection mechanism exists for B. coddii in the absence of available Ni in the rhizosphere. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Hyperaccumulator plants may offer a sustainable treatment option for the remediation of metal-contaminated sites (mining activity, refinery emissions, waste disposal, fossil fuel combustion, and agricultural application of pesticides and biosolids) and also an opportunity to mine naturally metal-rich soils i.e., phytomin- ing of ultramafic soils (Brooks et al., 1998; Angle et al., 2001; Li et al., 2003). Berkheya coddii Rossler is a Ni-hyperaccumulator plant that has attracted particular attention because of its high Ni con- centration and rapid biomass production. Robinson et al. (1997) reported an annual biomass production of 22 t ha −1 and up to 1% (w:w) Ni in the above-ground biomass. The combination of these two traits is rare and makes this plant suitable for the remedia- tion of Ni-contaminated soils by means of phytoextraction. Even Abbreviations: LA-ICP-MS, laser ablation combined with inductively coupled plasma mass spectrometry; DMG, dimethylglyoxime; ICP-OES, inductively coupled plasma optical emission spectrometry; XRF, X-ray fluorescence. ∗ Corresponding author. Present address: Hydrogeology Department, Helmholtz Centre for Environmental Research - UFZ, Permoserstraße 15, 04318 Leipzig, Germany. Tel.: +49 341 235 1982; fax: +49 341 235 451985. E-mail address: ahmad.moradi@ufz.de (A.B. Moradi). though some aspects of metal uptake by hyperaccumulator plants are already known (Kramer et al., 1996; Hall, 2002), these mecha- nisms might be different among different plants. Unravelling these mechanisms and interactions is necessary in order to improve phy- toextraction and phytomining techniques of Ni from contaminated and naturally-rich soils (McNear et al., 2005). The highest Ni concentration occurs in the shoots of hyperac- cumulators. Therefore, shoots and particularly leaf tissue has been the subject of previous investigations (Robinson et al., 2003; Bhatia et al., 2004; Budka et al., 2005; Berazain et al., 2007; de la Fuente et al., 2007; Tappero et al., 2007; Moradi et al., 2009). Proton or nuclear microprobe analyses of B. coddii collected from native South African ultramafic soils showed that Ni was concentrated in the mesophyll and epidermis of the leaves (Mesjasz-Przybylowicz et al., 2001). Although roots are the prime site of uptake of metals, the distribution of Ni in root tissues of B. coddii has rarely been investi- gated. Most research regarding Ni hyperaccumulation and uptake has been carried out on Ni hyperaccumulator plants of the fam- ily Brassicaceae and it is unclear whether other hyperaccumulators have the same uptake mechanism and distribution pattern as the Brassicaceae family (Robinson et al., 2003). Methods currently used for spatial localisation of metals within biological tissues are primarily micro analytical techniques based 0098-8472/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2010.02.001