Dimethylglyoxime (DMG) staining for semi-quantitative mapping of Ni in plant tissue

• Published in: Environmental and experimental botany Vol. 71; no. 2; pp. 232 - 240
• Main Authors: Gramlich, Anja, Moradi, Ahmad B., Robinson, Brett H., Kaestner, Anders, Schulin, Rainer
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.06.2011; Oxford; New York, NY: Elsevier Science; Elsevier
• Subjects: Berkheya coddii; Biological and medical sciences; Dimethylglyoxime (DMG); Fundamental and applied biological sciences. Psychology; Ni hyperaccumulator; Semi-quantitative Ni staining; Berkheya coddii; Semi-quantitative Ni staining; Dimethylglyoxime (DMG); Ni hyperaccumulator; Plant tissue; Cartography; Botany; Hyperaccumulator; Plant ecology; Staining; Semiquantitative
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2010.12.008

▶ We developed a DMG-staining tool for Ni distribution analysis in tissues of hyperaccumulator plants. ▶ We describe how image analysis provides a semi-quantitative map of Ni distribution in plant tissues. ▶ A spatially resolved distribution pattern of Ni in various tissues of Berkheya coddii was obtained. ▶ The method allows comparisons of Ni allocation between different hyperaccumulator plant species. Determination of the nickel (Ni) distribution in tissues of hyperaccumulator plants aids in understanding the strategies and mechanisms used by these plants to take up Ni from soils. Commonly used methods for measuring Ni distribution in plant tissues require expensive equipment and complex sample preparation. We tested a suite of staining methods consisting of dimethylglyoxime (DMG) dissolved in a range of solvents for the mapping of Ni distribution in the Ni hyperaccumulator Berkheya coddii Roessler. The best solution was DMG (10gl−1) dissolved in borax (25mM) and KOH (30mM). Plant tissue cross-sections were imaged under a microscope immediately after DMG application. A Karhunen–Loeve transformation was applied to the images to minimize interference from colours of other origin, e.g. from chlorophyll. The distribution of Ni could be determined at the cellular level and consistent patterns were obtained for replicates. Staining of Ni dissolved in agar at various concentrations was used to calibrate the method. Concentrations as low as 50mgkg−1 (fresh weight) could be detected. Averaged over several cross-sections the DMG method systematically gave lower concentrations than ICP-OES analysis of the respective plant part, indicating that not all Ni in the tissue reacted with DMG, but only Ni that is readily available. The DMG method may be used in conjunction with spectroscopic methods to resolve biologically active Ni.