THE INTERFACE BETWEEN FUNGAL HYPHAE AND ORCHID PROTOCORM CELLS

Seeds of the orchids Platanthera hyperborea, Spiranthes lacera, and Sp iranthes sinensis were germinated in vitro in the presence of compatib le fungal species and the resulting colonized protocorms were studied by light microscopy, transmission electron microscopy, and colloidal-g old affinity techniques. Protocorm cells in early stages of colonizati on contained coils of fungal hyphae (pelotons) separated from host cel l cytoplasm by the host plasma membrane and interfacial matrix materia l. Best cell walls were labelled by the colloidal gold - cellobiohydra lase I (CBH-I) complex to detect cellulose and, particularly over the middle lamella, by antibodies that bind to pectins (JIM 5 and JIM 7). A polyclonal antibody that binds to beta-1,3-glucans labelled the fung al cell wall heavily. None of the probes, however, labelled the interf acial matrix between the wall of active fungal hyphae and the surround ing plasma membrane. In contrast, the interfacial matrix material that ensheathed collapsing hyphae showed labelling after treatment with JI M 5, the polyclonal antibody, and the CBH-I complex. Labelling of host cell walls and fungal walls was similar to that described for early s tages.