| Abstract: | Sexual organs develop in the hermaphroditic, heterothallic ascomycete Ascobolus stercorarius only when strains of opposite mating-type are paired under appropriate conditions. A previous study of the two reciprocal compatible interactions, A-antheridial/a-ascogonial and a-antheridial/A-ascogonial, revealed several differences between them. The present study of the induction of antheridia has uncovered several other differences. Such induction occurred on severed hyphae, non-germinated oidia and germinated oidia of mating-type A but not of a under two different sets of conditions: (1) when such elements were placed on an agar medium containing only the secretions of a compatible mycelium, and (2) when they were in close proximity to a second group of compatible non-germinated or germinating oidia on an agar surface. This tendency for vegetative elements of A to differentiate as male structures more readily than those of a is consistent with the previous observation that the interaction of A-antheridial/a-ascogonial is generally the more vigorous one. It may also be responsible for a condition approaching functional sexual dimorphism in many mixed (A + a) mycelial cultures. |
