Utility of epi-illumination light microscopy for wood identification

Summary Wood identification is a crucial step to verify claims of the legality of wood and wood-derived products for compliance with the laws against illegal logging. For accurate determination of wood species, transmitted light microscopy has been utilized to identify microscopic features of wood from microscopic slides with thin sections from the transverse, radial, and tangential planes. When there are many woods in trading for identification, producing microscopic or permanent slides can be problematic because the production of the slides is time-consuming and slows down wood identification. However, the slides are not required for alternative microscopy such as epi-illumination light microscopy. In this study, we suggest the utilization of epi-illumination light microscopy as an alternative method to conventional transmitted light microscopy with microscopic slides for wood identification. We investigated the performance of selected epi-illumination light microscopic techniques: brightfield reflected light microscopy with a polarizer (RLBF), darkfield reflected light microscopy (RLDF), and fluorescence light microscopy by observing intervessel pits and vessel-ray pits. Among the selected epi-illumination light microscopy, brightfield reflected light microscopy with a polarizer produced images with small details and high contrast. Since sample preparation for reflected light microscopy can be minimized, we can accelerate the wood identification process without sacrificing accuracy. We confirmed that reflected light microscopy has sufficient performance with simple sample preparation comparable to transmitted light microscopy.