Physical forces supporting hyphal growth.

Hyphae are viscoelastic tubes whose internal pressure pushes the cell membrane against the inner surface of the cell wall. Catalytic yielding of the wall allows this turgor to force its polymers apart as new materials are added to the surface of the growing tip. Turgor drops slightly as the wall expands, creating a pressure gradient that causes the cytoplasm to flow toward the tip. These physiological processes affect the rate of extension of the hypha and determine the magnitude of the force that it uses for invasive growth. This paper provides an overview of the experimental basis for this description of hyphal mechanics and explains the wider significance of biophysical studies on fungi and water molds.