Seasonal variation of vessel pits in sapwood: microscopical analyses of the morphology and chemical components of pit membrane encrustations in Fraxinus mandshurica.

Encrustations undoubtedly cover the pit membranes in living F. mandshurica trees in winter and their morphology and chemical composition indicate that they are impermeable, have positional differences in function and are characterised by elaborate deposition/removal processes.