ABSTRACT
A stylized fungal organism is shown in Fig. 1.2, along with some of the properties that make it important in the context of this discussion. The mycelial portion of the fungus
consists of hyphae. These hyphae, which are absent in the Chytridomycetes and yeasts, are a filamentous assemblage of tubular cells in which continuity is maintained between adjacent cells by the absence of crosscell walls (septa) or a septum perforated by a pore. The hyphae thus develop as a coenocytic structure, consisting of continual cytoplasmic connectivity between adjacent cells. Hyphae average 5-6 µm in diameter and grow by wall extension at the tip (Rayner, 1991). Because they have a narrow diameter and long length, fungal hyphae present a large surface area, relative to volume, to the environment around them (Table 1.2). This property allows fungi to optimize the absorption of degradation products of simple carbohydrates and mineral nutrients that are derived from the action of extracellular enzymes produced by the fungi. Fungal hyphae may grow independently or coalesce to form larger and structured assemblages called rhizomorphs or strands. These
Hyphal diameter 5 µm
Hyphal dry weight 10% of fresh weight
1 cm3 of packed myceium 4×104 m
1 g fresh weight mycelium 2.7×104 m
1 g dry weight mycelium 2.7×105 m
Surface area per g dry weight mycelium 4.2 m2
Source: After Harley (1971).
