This review gives a retrospective of what is known about photoperiodism in
fungi, which is largely based on reports about seasonal spore concentration
s. Relatively few species have been investigated under laboratory condition
s, so that our knowledge whether seasonal reproduction in fungi is mainly a
direct response to environmental conditions or whether it involves a photo
periodic machinery with memory capacities and a relationship to the circadi
an system is extremely limited. To form a basis for further experimental en
deavors into fungal photoperiodism, we review the reports about endogenous
rhythms and photobiology. Finally, we will look at the possibilities of usi
ng the fungal circadian model system of Neurospora crassa for future work o
n photoperiodism.