Application of SEM/EDX and micro-SRXF analyses to describe metals distribution in Zea mays organs and tissues

A complete analysis was performed utilising scanning electron microanalysis to describe metals distribution in Zea mays, within the framework of the INCO-EU project "FERTILIA". Thin dried cross sections of roots and stems were analysed. A set of points for the different tissues were scanned and processed with the semi-quantitative analysis to check for macronutrients Ca, K, P, Mg, Cl, micronutrients Cu, Zn, Fe, Si, and toxic metals as Cr and Pb. Dot-maps of the same elements were acquired on representative sections from each specimen. Micro-SRXF (Synchrotron Radiation induced X-ray micro-Fluorescence) analyses of samples from the same plants were performed at the LURE (Laboratoire pur l'Utilisation du Rayonment Electromagnetique). Maize stems and roots sections were analysed fresh at the 1315 beamline. Elements distributions in each sample was plotted on 2D or 3D map. Both types of analyses, evidenced that Ca and K were the most abundant elements. Good agreement between data from SEM/EDX and mu-SRXF analyses was established utilising tissues labelling through the ubiquitary element Ca. Root periderm, root cortex and stem parenchyma showed the highest metal concentrations. The Ca content was utilised for the semiquantitative microanalysis to clear out possible 'outsider' spots among the measured points.