Morphogenesis of conidiomata in Chaetomella acutiseta (Coelomycetes)

Abstract

Developmental and ultrastructural aspects of conidiomata (pycnidia) in Chaetomella acutiseta var. acutiseta were examined in pure culture and on sterile oak leaves. The earliest recognized sign of pycnidial formation in this fungus is the aggregation of hyphae at the base of an erect seta. Subsequently, the hyphae adjacent to the seta become intermingled and then orient themselves parallel to one another as they rise up from the surface of the substrate. Additional setae form about the perimeter of the young pycnidium. Ontogenetic features of the cavity of conidiomata were examined by cryo-sectioning. As the pycnidium enlarges, the internal hyphae become more loosely packed and then differentiate into conidiophores bearing phialides.