Effect of Light Regimens and Intensities on Morphogenesis of the Discomycete Pyronema domesticum

Abstract

SUMMARYPyronema domesticum was cultured with daily cycles ranging from constant light to constant dark in combination with light intensities ranging from 150 to 0.15 fc. Light is required to initiate gametangial formation. A cyclical exposure to 150 fc for 6 h to 75 fc in constant light will allow the full expansion of most ascogonia. Production of poorly expanded or morphologically abnormal ascogonia increases with decreasing exposure to light. Under unfavorable conditions, juvenile gametangia or malformed small ascogonia predominate. Development of the ascogenous hyphae, asci, ascospores, and maturation of ascospores were generally favored by exposure to the higher light intensities for longer cyclical periods. Maximum production of apothecia with ascospores was found in those cultures exposed to constant light at 150 fc. The highest proportion of apothecia with matured ascospores occurred after exposure to 6-h light cycles at 150 fc with only 12.5% of the agar surface exposed to the light. Development of the sterile components (excipular hairs, paraphyses, and globular cells in the medullary excipulum) was favored by the shorter light cycles (4-6 h daily) and moderate light intensities. Inhibition of the sterile components was especially evident in cultures fully exposed to constant light at 150 fc. Maximum apothecial expansion was obtained with 6 h light daily with exposure to 75 or 150 fc. Sclerotia or sclerotial initials were formed when the cultures were grown in the dark or with low light intensities.