Light microscopy of wood using sanded surface instead of slides

Abstract

Xylem anatomy is fundamental in studies of the evolution of terrestrial plants, tree ecophysiology, forestry, and wood science. Traditional xylem anatomical studies by light microscopy utilize wood sections. However, the procedures are laborious, and high-quality histological sections have been particularly challenging to achieve from recalcitrant wood species and dry wood material. Modern microscopy offers opportunities for speeding up the xylem anatomical preparations. In this regard, the merits of using a sanded surface for wood anatomical research have been largely overlooked. Sanding of wood surfaces is practiced in dendrochronology and wood identification studies exclusively for the investigation of macro features, such as tree rings, wood porosity, or parenchyma patterns. We conducted microscopic level investigations of sanded surfaces of difficult-to-section high-density woods such as Dalbergia and Quercus species by reflected white light and epifluorescence microscopy. Reflected white light or combinations of reflected light and fluorescence could clearly show xylem micro-features in sanded wood surfaces. The resolution of cell types after sanding with 1000-grit was similar to the resolution obtained by transmitted light microscopy in histological slides. The advantages of sanded wood surfaces compared to traditional wood sections can be summarized as cost- and time-effective sample preparation, large sample area, intact cell walls and tissue structure, preservation of chemical content and extractives, and even focus of the field of view. A simple procedure of wood sanding instead of microscopic slides can be used for xylem microscopy and automatic image analysis of xylem structure.