Some Physiological Characteristics of Ascospore Activation in Neurospora crassa

Abstract

A number of compounds able to activate ascospores in high dilution (1 ppm or less) all contain an un-saturated ring, the most active a furan ring; often a CHO group. In such chemical activation spore age plays a critical part; within 3 weeks of shedding there is a "ripe" period during which sensitivity to activation is high, thereafter it declines. Activation by heat is much less dependent on age, possibly because heat induces a 2nd non-activating effect, simulating "ripeness". The results of reactivation after a forced return to dormancy also vary with the type of activating agent, and with the spore history. Several inhibitors were investigated (5-nitrofurfural, 2-4-dinitrophenol, NaHSO3, NaN3); the inhibition of activation caused by NaN3 can be reversed by furfural.