Abstract:Chinese white poplar plantlets from tissue culture were served as host plant in order to understand the mode and approach of infection and colonization of Chaetomium globosum ND35 on host plant. Infection of C.globosum ND35 ascospores on Chinese white poplar plantlets after germinating and colonization of C.globosum ND35 hyphae in poplar root were investigated by means of light microscopy, scanning electron microscopy, transmission electron microscopy and with immunofluorescent labeling. The results showed that hyphae of C.globosum ND35 invaded poplar root and stem from gap of epidermal surface cells, or directly penetrated epidermis by penetration peg formed from appressorium after ascospores germinating; and invaded poplar leaves mainly from stomata. Hyphae invaded root of poplar mainly colonized in the epidemic cells, the outermost cortical layer cells or intercellular spaces of cortical layer which was not found in endodermis and vascular tissues.