Visualization of the internal ultrastructure of lichens using cross-sectional polishing SEM

Abstract

Lichens, symbiotic organisms consisting of fungi and algae, are commonly found on various hard surfaces. Due to the challenges of preparing ultrathin sections of lichens embedded in minerals, electron microscopy (EM) has been mainly limited to surface analysis. To overcome this limitation, we present a "cross-sectional polishing SEM method". This technique involves embedding lichens in resin, cutting cross-sections with a band saw, mechanically polishing them, and observing the surface by scanning electron microscopy (SEM). By applying this method to a lichen-covered rock, we successfully obtained detailed cross-sectional images revealing the internal structure of the symbiotic algae and fungi, as well as the mineral substrate. This innovative approach provides a valuable tool for studying the internal anatomy of lichens, especially those growing on minerals.