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Title: Factors affecting growth of the arbuscular mycorrhizal fungal mycelium
Author: Ralph, Mary-Louise
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Arbuscular mycorrhizal relationships link plant root systems and zygomycetous fungi from the family Glomales in a symbiotic association which provides a carbon source to the fungus and benefits to the plant in terms of nutrient and water acquisition, and disease resistance. Root system colonisation is characterised by the formation of intracellular hyphae and internal fungal structures, the arbuscles and vesicles. Colonisation occurs after root penetration by fungal hyphae originating from either spores or extra-radical hyphae. The extra-radical hyphae, which form the fungal mycelium in the soil and have a primary role in host plant nutrition, are a largely neglected feature of the symbiosis due to the difficulties involved in their study. In the present work, methodologies were developed to allow in vitro studies of extra-radical hyphae and thus circumvent problems associated with the inaccessibility and opacity of the soil environment. Root pieces colonised by the arbuscular mycorrhizal (AM) fungus Glomus etunicatum were inoculated onto a dialysis membrane overlying transparent high purity agarose gel. This restricted the hyphae to a two-dimensional growth form which facilitated observation using microscopy and image analysis techniques, and enabled morphological measurements to be taken without the added complexity of three dimensional growth. The two major influences on AM fungal growth are those of soil and plant origin. The present work studied the effects of plant related factors on AM fungal hyphae. Host and non-host plant factors, and derivatives of these, were found to influence hyphal growth as characterised both by length measurements and morphological parameters. Host root exudates reduced hyphal growth, apparently as a result of changes in the overall distribution of hyphae within the mycelium, as measured by fractal dimension (FD). Non-host exudates and plant flavonoid compounds also decreased hyphal growth, but this result could not be attributed to changes in either branching or mycelial organisation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available