The effect of cytochalasin B on hyphal morphogenesis in Polyporus biennis

Cytochalasin B inhibited the radial growth rate of Polyporus biennis, and caused an increase in hyphal density through a reduction in the distance between successive branches. Cytochalasin B also produced irregular hyphal profiles and, in a small percentage of hyphae, forked apices. The position of clamp connexions was little affected by cytochalasin B, but the developmental process was specifically inhibited during initiation and during the last two stages, when contact and dissolution of the clamp were occurring. There were no major disruptions of the ultrastructure of the dolipore/parenthesome septum caused by cytochalasin B treatment.