Ultrastructure of conidiogenesis in Scopulariopsis brevicaulis

Abstract

An ultrastructural study of conidia and conidiogenous cells of Scopulariopsis brevicaulis (Sacc.) Bain. in various stages of development is presented using transmission and scanning electron microscope and freeze-etching techniques. Septa between both fertile and vegetative cells are examined. The development of the double septum is outlined and mechanisms are suggested to explain conidium secession. Cytological changes which occur in the developing conidium initial are illustrated and their possible association with wall synthesis and deposition is noted. Change in the orientation of rodlets occurs on the walls of frozen-etched conidia at different stages of formation. The relationship of this phenomenon to conidium development is discussed. Description of the nature of wall relations during conidium ontogeny is stressed because of its importance in a classification of Fungi Imperfecti based on developmental characters of the reproductive cells. A diagrammatic interpretation of the sequence of formation of wall layers of the developing conidium is presented.