Mycelia Within Organic Substrata

There is little information on mycelia within organic resources. Exceptions are maps of the extent of mycelia, inferred from interaction zone lines (see Chapters 7 and 11), and location of hyphae in relation to type of rot (Rayner and Boddy,

1988). The size of mycelia ranges from a few millimetres to many metres, in the case of longitudinally extensive (30 m or more) primary colonizers of attached branches and standing trunks (Boddy, 2001). The three-dimensional shape of the mycelial boundary is largely governed by the anatomy of the resource and by surrounding antagonistic fungi. For example, in wood, decay columns tend to be larger longitudinally than in other directions, reflecting difficulty of radial and tangential spreads. The diamond shaped cankers on sycamore (Acer pseudoplat-anus) caused by Gibberella Zeae (Ascomycota) result from spread between nutrient rich ray cells (Bevercombe and Rayner, 1980). Crucially lacking, however, is knowledge of the interconnectedness of different parts of the mycelium, and even the amount of mycelial biomass at different locations within organic resources. That there is spatial heterogeneity of mycelial distribution within wood decay columns is suggested by the common observation that when wood is incubated in a humid environment mycelium often grows out rapidly and profusely from the edges, and more slowly and less densely from more central regions.

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