Arbuscular Mycorrhizal Fungi of Abandoned Agricultural Land and their Implications for the Restoration of Puget Sound Prairies

Arbuscular Mycorrhizal Fungi (AMF), members of the Glomeromycota, are by far the most widespread of the mycorrhizal fungi (Brundrett 1991) occurring in 80% of all plant species (Smith 1997). Morphologically, these fungi are a network of hyphae that grow within the roots of plants and extend out into the soil. Unlike the ectomycorrhizal fungi, AMF actually penetrate the walls of root cells and form intracellular structures. They produce two distinct structures: the saclike vesicles, which are thought to act as storage structures for lipids (Morton and Benny 1990); and densely branched or coiled hyphal masses called arbuscles, which act as the site of nutrient exchange between the plant and the fungus. These fungi were previously known as Vesicular Arbuscular Mycorrhizae. However, it has been shown that vesicles can be produced by nonmycorrhizal fungi and only arbuscles are unique to this group of fungi (McGonigle et al. 1990). There is evidence that the proportion of arbuscles to vesicles can be influenced by ambient nutrient levels and can act as an indicator of the level of benefit received by each partner of the symbiosis (Johnson et al. 2003).