An Action Spectrum for Light-induced Primordium Formation in a Basidiomycete, Favolus arcularius (Fr) Ames

The action spectrum for the initiation of fruiting (primordium formation) in Favolus arcularius was determined on the equal response basis. The detectable effect of light was observed in the region between 350 to 560 nanometers, showing six distinct peaks at 374, 398, 424, 446, 480, and 514 nanometers. The half maximum response is reached with 1.8 x 10(8) ergs per cm(2) at the most effective wavelength, 398 nanometers. Since the inhibitors, diphenylamine and quinacrine, had no consistent effect on the primordium formation, it is suggested that the possible photoreceptor pigment(s) may be neither carotenoid nor flavinoid.Comparing the action spectrum with those for some other fungi, the possibility that the photoreceptor system of this fungus may consist of two pigments is discussed.