Spore discharge rhythms in pyrenomycetes: VI. The effects of climatic factors on seasonal and diurnal periodicities

Abstract

Seasonal and diurnal periodicities of spore discharge have been determined in seven lignicolous pyrenomycetes, using a Hirst spore trap. Hypoxylon rubiginosum, H. fragiforme and Lasiosphaeria spermoides had peak discharge periods in October, Eutypa acharii in May, Diatrype disciformis in April–May, Diatrypella quercina in September and Diaporthe sp. in August. No spores were discharged by Hypoxylon fragiforme during late February to early April, none by Diaporthe sp. during November-January, and none by Diatrypella quercina in March. Analysis of spore counts and climatic data indicated a positive correlation between spore discharge and rainfall except in Lasiosphaeria spermoides (discharge correlated with humidity) and Eutypa acharii (discharge correlated with duration of sunshine). All the species have diurnal rhythms with nocturnal peaks except E. acharii, in which the spore discharge rate fluctuates more rapidly producing early morning and afternoon peaks. Spore discharge rhythms are considerably modified from time to time by climatic factors, particularly rainfall.