Effects of humidity and rainfall on spore discharge rhythms in pyrenomycetes

Abstract

In five coprophilous and two lignicolous pyrenomycetes maximum spore discharge rates occurred at lower humidities (35 or 48% r.h.) except in Pleurage taenioides (at 78% r.h.). In species of Sordaria and Podospora, spore residues at different humidities were complementary to numbers of spores discharged so that total spore productivity remained fairly constant from 35 to 99% r.h. In Pleurage species, productivity was smaller at low humidities. No evidence was obtained of entrainment of spore discharge rhythms by alternating high and low humidities, but the amplitude of the rhythm was generally greater than under constantly humid conditions. Rain increased productivity of perithecia by prolonging the period of activity. It also increased the amplitude of the rhythm and produced wave-like oscillations in the rate of spore discharge which were closely associated with the timing of the successive rain periods. In the lignicolous species, rain produced an immediate spore discharge but there was no obvious correlation between the duration of the rain and the numbers of spores subsequently discharged.