Journal of Cell Science, Vol 11, 33-47, Copyright © 1972 by Company of Biologists

Submitted on December 9, 1971

A Fine-Structural Study of Conidium Initiation in Stemphylium Botryosum Wallroth

¹ Department of Biology, University of Oregon, Eugene, Oregon 97403, U.S.A

Conidia and conidiophores from synchronously sporulating cultures of Stemphylium botryosum were fixed and embedded at successive intervals for examination under the electron microscope.

The spore initial arises as a small bud at the tip of the conidiophore, and no discontinuity between the conidiophore wall and the spore can be detected. The single-celled bud and the tip cell of the conidiophore have very similar cytoplasmic features.

Besides the usual cellular organelles, irregularly shaped electron-transparent areas in which membrane systems seem to perform some internal secretory activity between the leaflets themselves are present. Globules of the slightly electron-dense material originating in these specialized areas can also be found next to the plasma membrane where they are released and presumably participate in wall formation. Such a secretory system has not been described before and may be of particular importance in higher fungi which are known to lack a true Golgi apparatus.