Morphological plasticity in fungi.

Fungi grow for the most part as hyphae extending at their tips. Hyphae aggregate into mycelia, the form of which is dependent on many factors but often on the density of tips which is a function of such factors as the degree of hyphal branching, anastomoses and tip and hyphal death. Some possible mechanisms behind these processes are considered. A particularly important element in tip growth and branching is the movement of protons across the plasma membrane. Certain rhythmic growth phenomena are discussed in these terms. Another important element in morphological development is water flow bringing about a redistribution of solutes within a mycelium and probably influencing wall hydration and wall extensibility. Finally, special consideration is given to development of basidiomycete vegetative mycelium where there are indications that cytoplasmic factors can modulate the expressions of the nuclear genome.