HISTOLOGICAL OBSERVATIONS OF ARBUSCULAR MYCORRHIZAL FUNGUS INFECTION TO ROOT-TISSUE OF ASPARAGUS-OFFICINALIS L SEEDLINGS

The infection process of arbuscular mycorrhizal (AM) fungus, Gigaspora margarita, in asparagus (Asparagus officinalis L.) Seedling roots was histologically investigated to clarify the mechanism as to how the or ganism enhances asparagus plant growth. Such information may lead to a better understanding of growth through symbiosis. The sequential infe ction process was classified into four main stages. Stage I: a hypha p enetrated into the host roots via the intercellular spaces of the epid ermal cells to the cortex. Stage II: the hypha initially elongated lon gitudinally in the outer cortex and then in the inner cortex. Stage II I: the hypha invaginated to the surface layer of the cortical cell; at the invaginating point, the primary cell wall became thin and indisti nguishable; the secondary cell wall also became thin but remained visi ble. after invaginating, the hypha formed a ramified arbuscule which p ushed the host cell plasmalemma inwardly but did not crush it No hypha penetrated the endodermis. Stage IV: the arbuscule collapsed into a m ass. This study clarified the histological characteristics of host cel l wall and middle lamella during an infection by the AM fungus (Gigasp ora margarita) in asparagus seedling roots.