The Ultrastructure of Soft Rot Fungi. I. Fine Hyphae in Wood Cell Walls

ABSTRACT

Three soft rot fungi were studied with respect to the ultrastructure of fine hyphae in wood cell walls. Inoculated birch sections showing different stages of cell wall attack were prepared for TEM using four fixation procedures. Comparisons were made between fine penetration, T-branch and proboscis hyphae. Fine hyphae of Phialophora hoffmannii have a cell wall; this was absent at hyphal apices of Humicola alopallonella and Monodictys putredinis. An electron-opaque region or halo found in the wood cell wall around all fine hyphae may be a pre-cellulolytic system secreted by these hyphae. Fine soft rot hyphae have a simple organelle composition, but T-branch and proboscis hyphae have membranous organelles thought to be derived from mature parent hyphae.

Key Words:

• wood decay
• soft rot fungi
• Phialophora
• Humicola
• Monodictys
• hyphal ultrastructure