plural mycorrhizae the usually symbiotic association between higher plant roots (host) and mycelia of specific fungi that aid plants in the uptake of water and certain nutrients and may offer protection against other soil-borne organisms —note mycorrhizal types include ectotrophic (ectomycorrhiza), endotrophic (endomycorrhiza), and ectendomycorrhiza —see rhizomorph This definition last updated 07/20/2008