Abstract:Endophytic mycorrhizaI fimgus P15 isolated from the roots of wild Cymbidium e nsifolium was used to infect the non-mycorrhizal rhizomes of C．sinense and C. ensifolium. A marked increase in respiratory rate，cytochrome C oxidase activity，and peroxidase activity was shown in the rhizomes of two infected species，while the change in IAA oxidase activity was slight．The levels of respiratory rate，activities of cytochrome C oxidase and peroxidase in the rhizomes of C. ensifolium, were all higher than those of C. sinense before or after infection, but the IAA oxidase activity showed the contrary．