The Ultrastructure of Soft Rot Fungi. I. Fine Hyphae in Wood Cell Walls
| Autor: | Michael D. Hale, Rodney A. Eaton |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
0106 biological sciences
0301 basic medicine Hyphal growth Mycelial cord Hypha Physiology fungi Hyphal tip Cell Biology General Medicine 030108 mycology & parasitology Biology 010603 evolutionary biology 01 natural sciences Cell wall 03 medical and health sciences Botany Ultrastructure Genetics Cinemicrography Molecular Biology Mycelium Ecology Evolution Behavior and Systematics |
| Zdroj: | Mycologia. 77:447 |
| ISSN: | 0027-5514 |
| DOI: | 10.2307/3793202 |
| Popis: | 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 pen? etration, 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. The characteristic features of wood decay by soft rot fungi have been described previously and the progressive invasion and decay of wood cell walls by Phialopho? ra hoffmannii (Van Beyma) Schol-Schwarz and P. fastigiata (Lagerb. & Melin) Conant have been monitored using time-lapse cinemicrography (Hale and Eaton, 1985). After the colonization of wood surfaces by soft rot hyphae, the process of decay is initiated by the penetration of fine hyphae through wood cell walls. The penetration process shows many similarities to that occurring with some blue stain fungi. The process of blue stain penetration was thought to be primarily by mechanical pressure (Liese and Schmid, 1961, 1964) although Liese (1970) sug? gested that the penetration was achieved by localized enzymatic action at the hyphal tip with mechanical pressure pushing it through the cell wall. Decay of wood by soft rot fungi occurs either through erosion of the wood cell wall by enzymes released from hyphae on the lumen surface of the wall or by the excavation of cavities around hyphae in the S2 region ofthe cell wall. The establishment of fine hyphae within wood cell walls prior to cavity formation is considered here. Cavities are initiated by fine hyphae which grow in the wall and are then oriented parallel to the cellulose microfibrils. Krapivina (1960) showed that this initial process may happen either by a change in the direction of growth of the penetration hyphae to form L-bending hyphae (Levi, 1965; Nilsson, 1974a, b) or by branching, with each branch growing in the opposite direction, a process Corbett (1965) termed "T-shaped branching." Corbett and Levy (1963) only ob? served T-branches in the second S2 cell wall layer but T-branches have since been observed in the first S2 layer (Levy and Stevens, 1966). After a period of apical extension within the cell wall, hyphal growth ceases and a cavity is created by enzymatic activity along the length of the hyphae. During the formation of the cavity, the diam of the hypha increases. The emergence of a fine hypha, termed the proboscis hypha, is followed by a linear rate of growth within the cell wall, cessation of apical extension, and the formation of a cavity around the hypha, which also increases in diam. A series or chain of cavities is produced by repeated emergence of proboscis hyphae at |
| Databáze: | OpenAIRE |
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