Investigation of the extracellular mucilaginous materials produced by somewood decay fungi

The morphology of the extracellular mucilaginous material (ECM) produced by Coniophora puteana and Coriolus versicolor during colonization of Scots pi ne and beech was studied using SEM. Wood specimens were examined in the fro zen hydrated (FH) condition using low-temperature SEM, and in the freeze-dr ied (FD) and critical point dried (CPD) state, using conventional SEM. All techniques produced artifacts but the ECM was best preserved when examined in the FH state. Very little difference was observed between FH and FD prep arations, but critical point drying damaged the ECM extensively Copious amo unts of ECM were produced by both fungi. It was found to line much of the l umen surface, establishing contact between the mycelium and the wood substr atum. Most aerial hyphae were coated with ECM, appearing glued together in a bundle-like fashion. The ECM thickness varied within the same wood cell a nd from one cell to another. A peculiar granular pattern, in which the ECM was definitely involved, was seen on occasion to encircle the infecting hyp hae where they contacted the wood surface. Other morphological patterns of ECM distribution were also observed. Calcium oxalate crystals of varying sh apes and sizes were often seen associated with the mycelia and mucilage of the two fungi in beech but not in Scots pine. The probable roles played by the ECM in wood decay mechanisms are discussed.