Effect of light on the initiation of pileus formation in a basidiomycete, Favolus arcularius

Pileus formation in Favolus arcularius is induced by light,but no photoinduction occurred in young epileate stipes. Thestipes usually had to attain a length of about 5 mm to be photosensitive.Synchronous pileus formation could be induced by exposure tolight using epileate stipes which had been preincubated in darknessfor 48 to 72 hr. The pileus primordium formed about 24 hr afterthe start of illumination, however, continuous illuminationwas not necessary to produce this effect. A dark period givenbetween 1 and 8 hr after the start of illumination did not retardpileus formation. The photoinduction of pileus formation involvedtwo light-requiring processes, one occurring during the firsthour (the first light process) and the other from the 8th tothe 24th hr (the second light process). The photoresponse inthe first light process was saturated with 5 lux of light, buta light intensity below 1 lux was essentially ineffective. Onthe other hand, the reaction in the second light process couldbe started by less than 2 lux, and was accelerated by increasingthe light intensities up to about 150 lux. Further increasesin light intensity did not improve any significant effect. (Received April 30, 1974; )