The effects of polyoxin on sensitive and resistant isolates of Alternaria In the resistant isolate, similar mycelial changes were observed but frequency of these changes was much less than in the sensitive one.

The effects of polyoxin on mycelia of Alternaria kikuchiana Tanaka were observed with an optical microscope.The effects were roughly classified into four types, i) induction of characteristic bulbous structure at the hyphal tip and on the lateral hyphal wall, ii) induction of intrahyphae in relatively older hyphae, iii) acceleration of septation in relatively older hyphae, and iv) accleration of pigmentation in a whole mycelium. The above observations suggested that polyoxin might have several effects on this fungus in addition to the inhibition of chitin synthesis of the hyphal cell wall.

The effect of polyoxin on spore germination of A. kikuchiana Tanaka was investigated using transmission and scanning electron microscopes. The entire spore was covered by two-layered cell wall, having a rough surface. During the initial stages of germination, the new cell wall layer being continuous with the spore inner wall layer was formed as the cell wall of germ tube. When the spore was treated with polyoxin, the entire germ tube swelled forming the bulbous structure and the outer layer occurred around the germ tube soon after the germ tube emerged. If polyoxin was absent, such an outer layer did not appear during the incubation period.