Light-driven diurnal zonation in the filamentous fungus Fusarium solani.

Zonation in growing mycelia of Fusarium solani was induced by diurnal light/dark cycles. Only those parts of the hyphae that grew in darkness for less than 20 hours developed a zone of conidia after illumination. In continuous darkness, in continuous illumination, or after a transition from light to darkness, a conidiation zone failed to appear. Only light periods exceeding a few seconds but lasting less than 21 hours during a 24 hour light/dark cycle induced zonation. This zonation was not caused by periodic staling of the growth medium.