Nutrient translocation in fungi has recently been covered in several reviews (Cairney, 1992; Boddy, 1993; Jennings, 1994; Cairney & Burke,1996). This chapter adds some new results and discusses nutrient translocation and electric signalling as parts of the integration of activities within the fungal mycelium. Some parts of the chapter are rather speculative but this is meant both to provoke the reader to come up with better ideas and to encourage more people to start research into the subjects of this chapter.

Discussion of definitions: colony and mycelium. A suggestion for using the terms Functional Mycelium Unit and Genetic Mycelium Unit

What is a fungal colony and what is a fungal mycelium? According to Ainsworth & Bisby's Dictionary of Fungi (Hawksworth et al., 1995) a fungal mycelium is ‘a mass of hyphae’ and a fungal colony is ‘a group of hyphae which, if from one spore, may be one individual’. The definitions given by Jennings & Lysek (1996) are ‘ Mycelium = network of hyphae’ and ‘ Colony = the coherent mycelium of one origin’. However, Rayner argues that the mycelium is a functional unit, an individual (Rayner, 1991). It seems we ought to see the mycelium and the fungal colony as they have been discussed historically, as a mixture of two distinctly different concepts.

1. Genetically identical hyphae occupying a continuous space, the Genetic Mycelium Unit (GMU).

2. The network of functionally integrated hyphae that forms an individualistic organism, the Functional Mycelium Unit (FMU).