Introduction

Water is required by fungi for growth and for movement of solutes within the mycelium (translocation). Many aspects of reproduction are governed by water availability; for example, spore release and dispersal are dependent on it, as discussed in the classic text by Ingold (1971). In the past 20 years, there has been little to modify what is described there. However, now there is a better idea of spore release in some of the lower fungi (see, for example, Duniway, 1979; Gisi, Hemmes & Zentmyer, 1979; Gisi & Zentmyer, 1980; Money & Webster, 1988, 1989; Money, Webster & Ennos, 1988; Horn, 1989, 1990). Nevertheless, the water relations of basidiospore discharge are still a matter of controversy (Webster et al., 1988; Ingold, 1990; Corner, 1991). In this volume, I consider only the water relations of growth (this chapter) and translocation (Chapter 14). For terminology and background to this chapter the reader is referred to reviews by D. M. Griffin (1981), Eamus & Jennings (1986a), Papendick & Mulla (1986) and Jennings (1990c).

Growth

The general picture

When a fungal cell grows or a hypha extends, it increases its volume. Part of that increase in volume is brought about by the inflow of water. The rate of flow must be such that the pressure generated does not cause the wall to burst (Robertson, 1959, 1965).