Approaches to the study of the extraradical mycelium of arbuscular mycorrhizal fungi

Abstract

One of the most neglected areas of research on arbuscular mycorrhizas is the role of the extraradical mycelial network that links colonisation of the root by arbuscular mycorrhizal fungi (AMF) with the soil matrix. This hyphal network is a key component in nutrient cycling in natural ecosystems and constitutes a major sink for carbon and other elements. Several reviews have attempted to highlight this important area (Sylvia, 1990, 1992) and this has led to an increased interest in microcosm experiments that allow separation of roots from the developing mycelium of different AMF. Various rhizobox or cuvette systems have been developed and employed which allow growth of a plant root system in one compartment (Fig. 1) whilst allowing spread of the extraradical mycelium (ERM) of AMF through a nylon mesh screen (30–40m) into a root-free compartment (Jakobsen et al., 1992a; Li et al., 1991; Schüepp et al., 1987). In this review, therefore, we will attempt to highlight recent approaches taken to improve our knowledge of the ERM in terms of its development, functioning and activity for individual AMF. KeywordsArbuscular Mycorrhizal FungusMycorrhizal FungusArbuscular MycorrhizaExtraradical MyceliumExternal HyphaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.