MycorrhizaeThis article is part of a larger document. View the larger document here.
Mycorrhizae, a mutual partnership between certain soil fungi and fine root tips, contribute to tree growth and vigor by increasing both water and nutrient uptake, especially nitrogen (N) and phosphorus (P). The fungal hyphae increase root surface contact with the soil, while the fungi are supplied with a reliable source of carbon (Allen 1991, George and Marschner 1995). Two types of mycorrhizae are found on most trees-ectomycorrhizae (EM) and endomycorrhizae-also called vesicular-arbuscular mycorrhizae (VAM). The EM fungi are mainly mushroom-forming basidiomycetes, while the VAM fungi are Zygomycetes, most of which form microscopic underground spores. The majority of plants, including many trees, are colonized by VAM fungi, while EM are almost exclusively limited to woody species (Allen 1991, Mosse and others 1981). Some plants can have both VAM and EM fungi (Safir 1987.).