Ultrastructure of the Mycorrhizal Association Formed Between Zea Diploperennis and Glomus Fasciculatus

SUMMARY

Initial stages of mycorrhizal establishment were marked by development of intercellular hyphae ramifying between cortical cells. Penetration of cortical cells by the invading intracellular hyphae (endophytes) was accompanied by a thinning of the cortical cell wall and the formation of a “collar” around the endophyte. Arbuscules were formed by repeated branching of the endophyte. Host cell cytoplasm was never observed in direct contact with the arbuscular system but was separated by an interfacial zone consisting of the host plasmalemma, the interfacial matrix and the fungal cell wall. Deterioration of the arbuscular system began from the finer branches and proceeded backwards to the point of penetration. Septum formation was not observed. Deteriorated arbuscular material accumulated into clumps. Cortical cells did not appear to degenerate during arbuscular breakdown.