The long tubular branching hypha is the most important fungal growth form, although some fungi grow as discrete spherical or ellipsoidal yeast cells. Vacuoles are ubiquitous in yeast cells as well as in hyphae of filamentous fungi and can be readily stained by simple methods of dye uptake. They appear as spherical or tubular organelles of extremely variable size. Vacuoles are known or suspected to play several crucial roles in the physiology of vegetative growth. Only some of these roles are related to the activity of lytic intravacuolar enzymes. Thus, vacuoles can degrade redundant organelles, presumably recycling macromolecules, especially under conditions of nutrient starvation. They are also the destination of endocytotic vesicles originating by inward budding of the plasma membrane, thereby providing a mechanism of ‘face-lifting’ of the plasma membrane and a means of communication with the extracellular environment. Further, vacuoles store organic and inorganic nutrients, and they may detoxify the cytoplasm by sequestration of toxic substances.
