Applications of Environmental Scanning Electron Microscopy (ESEM) in botanical research

Abstract

Conventional Scanning Electron Microscopy (SEM) is limited by artefacts from sample preparation, while Environmental Scanning Electron Microscopy (ESEM) permits observations of hydrated, non-conductive samples without any preparation. In this short review, the two systems are described and some examples given. In addition, a study of trace element localization by X-ray ESEM microanalysis in Azolla caroliniana cultured in the presence of trace elements is presented. The highest concentration occurred in roots and stem. Leaves showed lower accumulation, with concentrations decreasing from the base to the apex of the shoot, and sharp differences between ventral and dorsal lobes of single leaves, the former accumulating more than the latter. The epidermal cells in the ventral lobes of basal leaves were largely lost in treated plants. The differential localisation of trace elements in the plant protected the dorsal lobes, which are the main photosynthetic part of the plant, the nitrogen-fixing cyanobacterial colonies and the apical meristems from potentially adverse effects of trace elements.