Ultrastructure of conidium germination of Cochliobolus carbonus

Abstract

Multiseptate conidia of Cochliobolus carbonus germinate in water by one or two polar germ tubes. The septa between cells within a conidium contain a central pore, which is plugged before germination but open during germination, so that all cells are interconnected. During germination, vacuoles enlarge, endoplasmic reticulum profiles increase in number, and mitochondria change from a spherical form with loosely arranged cristae to an elongated form with closely packed cristae. The conidium wall consists of an inner electron-translucent layer and an outer electron-opaque layer. The germ tube wall is continuous with the innermost layer of the conidium wall. Shortly after germination, a septum with a central pore forms in the germ tube by invagination where it emerges from the conidium. The germ tube wall is surrounded by a fibrillar sheath. The presence of apical vesicles in the germ tube tip is confirmed. The associations of Woronin bodies with septal pores and microbodies, of lipids with vacuoles, and of microbodies with lipids and vacuoles are discussed.