Application of a membrane-gel procedure to determine the effects of root exudates on the growth of the extraradical hyphae of the arbuscular mycorrhizal fungus Glomus etunicatum

A technique was developed to allow in vitro studies of extraradical hyphae of the arbuscular mycorrhizal fungus Glomus etunicatum. Mycorrhizal root pieces were placed onto dialysis membrane overlying transparent high purity agarose gel. This restricted the hyphae to a two-dimensional growth form and permitted visualisation and measurement of hyphal proliferation, using light microscopy coupled with image analysis, in the presence of point sources of host plant root exudates. Fractal geometry was employed in mycelial description. Data showed that root exudates only affected the growth (length and fractal dimension) of the mycelium when positioned heterogeneously, as a point source.