Ultrastructure of conidiogenesis in Drechslera sorokiniana

Abstract

An ultrastructural examination of conidiogenesis in Drechslera sorokiniana reveals that conidia develop enteroblastically through channels in the conidiogenous cell wall. These channels probably form by autolysis of the outer wall layers. The data support earlier concepts based on light-microscopic studies of conidium ontogeny in this and other developmentally related species of hyphomycetes. The surface morphology and relationship of wall layers of the conidium and conidiogenous cell at various stages of development are illustrated by scanning and transmission electron microscopy, respectively. This information is summarized in a diagrammatic interpretation of conidiogenesis. Cytodifferentiation during conidium formation and conidiogenous cell proliferation is also examined. A possible association between organelle migration in developing conidiogenous cells and fascicles of microfibrils, proposed in an earlier paper, is discussed. A suggestive explanation is presented for the accumulation of microbodies in conidium initials and apices of proliferating conidiogenous cells. Layers of endoplasmic reticulum which are terminally hypertrophied and juxtaposed to the plasma membrane of developing conidiogenous cells are also noted.