(pl. ectomycorrhizae) symbiotic association between a nonpathogenic or weakly pathogenic fungus and the roots of plants with fungal hyphae between and external to root cells (see arbuscular mycorrhiza)
(Gr. ecto, outside) Mycorrhizas with hyphae that do not penetrate cells.
or ectotrophic mycorrhizae. A symbiotic condition between a fungus and the root of a plant in which the fungus forms a sheath around the root. Some hyphae connecting to this sheath penetrate the host root and spread through the soil surrounding the roots. Ectomycorrhizae form between tree species and basidiomyctete fungi.