Zooming into refractory timber: enhancing anatomical identification with confocal laser scanning microscopy and fluorescence

Summary Accurate wood identification is crucial for combatting the illegal logging and trade of forest products worldwide. However, certain challenges such as small specimen size, high wood density, and level of degradation can complicate the identification process. There is therefore a need to develop methods and use complementary techniques in forensic wood identification, particularly for difficult samples. This study utilized confocal laser scanning microscopy (CLSM) to detect and locate autofluorescence of axial parenchyma cells (APCs) to facilitate the identification of three challenging unknown wood specimens. These specimens posed difficulties for sectioning with a microtome due to brittleness, density, or small size constraints. CLSM results were compared with those from conventional light compound and stereomicroscopy. In our investigation, the three unknown wood samples were identified as Bobgunnia cf. fistuloides, Chlorocardium cf. rodiei, and Diphysa cf. carthagenensis. Specifically, CLSM confirmed the absence of apotracheal parenchyma in B. cf. fistuloides, which could not be determined using fluorescence stereomicroscopy. For D. cf. carthagenensis, CLSM’s fluorescence intensity highlighted axial parenchyma effectively, surpassing fluorescence stereomicroscopy. A notable advantage of our non-invasive CLSM method was its ability to examine smooth, unsectioned block surfaces, thereby enhancing preservation and ‘in-situ’ visualization of APCs. Our results combining autofluorescence and CLSM clearly offered superior resolution in observing APCs compared to traditional microscopy and can thus be applied for increasing confidence in wood species identification.