Histochemical observations on apothecia, permanently vegetative hyphae, and sclerotia of Pyronema domesticum with special reference to light

Abstract

The Discomycete, Pyronema domesticum (Sow. ex Gray) Saccardo was cultured on an inorganic salts medium, as well as on potato dextrose agar (PDA), and exposed to different light regimens. Permanently vegetative hyphae were obtained on PDA cultures illuminated with cycles of 12 h light: 12 h darkness, while abnormal confluent padlike apothecia were formed on PDA in constant light and sclerotia were formed in PDA cultures that were incubated in the dark. Apothecia were formed on the inorganic salts medium and exposed to different light regimens that favored either overall apothecial development or primarily favored development of the ascogenous or sterile system. Histochemical tests were conducted on permanently vegetative hyphae, sclerotia, and apothecia to localize glycogen, carbohydrates, mucilage, protein, DNA, RNA, lipids, and carotenes. Exposure to light stimulated synthesis of DNA, lipid, glycogen, and other carbohydrates. Favorable development of morphologically normal ascogenous hyphae and asci was positively correlated with moderate to high levels of DNA, RNA, protein, and PAS-positive substances (excluding glycogen). Conversely, favorable development of the morphologically normal sterile system was not positively correlated with higher levels of any components, but excessive accumulation of glycogen was associated with its unfavorable, limited development. Massive accumulations of protein, phospholipids, DNA, glycogen, mucilage, and other carbohydrates were observed in the nonsporulating asci in cultures maintained in the dark for 4 days before being exposed to constant light, or in the permanently vegetative hyphae.