Abstract Like all forms of microscopy, scanning electron microscopy (SEM) requires some sort of preparation before wood samples can be observed. Damage to the cell wall integrity during sectioning is a common but undesirable effect. Some artifacts are familiar to wood anatomists, while others are rare and may often be missed or mistaken for materials from external sources. In this study, SEM imaging revealed thin, filamentous and membranous structures that protrude into the lumina of tracheids in spruce wood. These structures were either partially or completely covering the tracheid lumen and showed a thread- or mesh-like morphology. Their presence was largely restricted to earlywood and occasionally associated with trabeculae. The samples did not reveal any distinct indication of fungal or bacterial presence. Therefore, we conclude that these structures are most likely cell wall material frayed from sample sectioning. Alternative explanations, such as extractive residues or biological origins, though could not be fully excluded and require further investigations. Nevertheless, the results emphasize the importance of awareness of artifacts during SEM analysis and careful consideration of unusual morphologies in wood anatomy.
Koddenberg et al. (Wed,) studied this question.