ELECTRON MICROSCOPY OF PHIALIDES AND CONIDIOGENESIS IN TRICHODERMA SATURNISPORUM

Abstract

Each phialide had a thick‐walled neck region located immediately below a light microscopically inconspicuous collarette. The thickened wall of the phialide neck was multilaminate, with layers of different electron transmission properties. A developmental stage in the formation of the first conidial initial was observed. Conidial initials blew out through the thickened neck region, increased in size, and were eventually delimited by centripetally developing septa. Mature, winged conidia had an electron‐opaque outer wall layer and an electron‐transparent inner wall layer. The wing was formed by separation of these outer and inner wall layers and buckling or wrinkling of the outer layer. As early as they could be discerned, conidial initials had developed the electron‐opaque wall layer which characterized mature conidia. Each conidium‐delimiting septum became bilayered; the upper layer formed part of the conidial base, and the lower layer became a portion of the wall of the next conidial initial. Phialides lacked an electron‐opaque wall layer, and they possessed areas of abundant rough endoplasmic reticulum, as well as free ribosomes. Lipid globules were also abundant, especially in conidia. The distinction between phialides and annellides was questioned.