Opposite morphogenetic changes have been provoked by growing A. arbuscula in the presence of two antimicrotubular agents: taxol maintained vegetative hyphal elongation growth and thereby prevented their apical differentiation into couples of male-female gametangia; nocodazole prevented germ tube outgrowth, induced emergence of epihyphal rhizoids and led to altered positioning of intrahyphal nuclei. Primary hyphal growth in the presence of taxol prevented the nocodazole-induced morphogenetic disturbance.