Apical vesicles and microtubules in rhizoids ofBlastocladiella emersonii: Effects of actinomycin D and cycloheximide on development during germination

Summary The ultrastructure of untreated germinating cells ofBlastocladiella emersonii was compared with that of cells inhibited by Actinomycin D and cycloheximide. The rhizoids and germ tubes of the fungus contained longitudinally oriented microtubules and apical clusters of cytoplasmic vesicles. The vesicles, apparently derived from Golgi apparatus equivalents also described in this paper, were involved in the tip growth of the germ tubes and rhizoids. Zoospores germinated in Actinomycin D encysted and developed short germ tubes containing microtubules and apical vesicles before further development was arrested. Zoospores treated with cycloheximide encysted but did not develop germ tubes.