Mapping of nickel in root cross-sections of the hyperaccumulator plant Berkheya coddii using laser ablation ICP-MS

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.