Morphological changes during the life cycle of A. pullulans can be controlied by the nitrogen source and this led to suggestion of a 6 subcycles of vegetative cycle
Subcycle 1 : Blastospores produced new blastospores by budding
Subcycle 2 : (presence of nitrate as nitrogen source): Blastospores continued budding to produce as aseptate chain of blastospores (pseudomycelium).
Subcycle 3 : (presence of ammonium nitrate as nitrogen source) : Blastospores differentiated into swollen cells (larger blastospores). Swollen cells can produce either one or more germ-tubes and give rise to a septate mycelium or septa.
Subcycle 4 : septate swollen cells gave rise to mycelium and blastospore or converted to thick wall chlamydospores (chlamydospores were not formed when ammonium ion was used as nitrogen source in the culture medium)
Subcycle 5 : Chlamydospores produced germ-tubes which developed to mycelium or blastospores. The mycelium and blastospores were capable of budding and transferred to sub-cycle 1, 2 or 3depending on the environmental conditions.
Subcycle 6 : The cells of mycelium produced dark pigment and thick wall converted to chlamydospores. The chlamydospores did not germinate unless transferred to a fresh culture medium.