Peculiarities of exogenous dormancy of Aspergillus niger conidia

Aspergillus niger conidia are characterized by exogenous dormancy: the firs t stage of their germination is accomplished in twice-distilled. water. How ever, germ tube formation requires the availability of carbon and nitrogen sources. Exogenous dormancy in A. niger conidia exhibits the following pecu liar features: (i) nitrogen-containing substances are active stimulators of germination; (ii) temperature-dependent changes in the lipid bilayer and i n the neutral lipid composition of conidia are virtually identical to those occurring in growing mycelium under temperature stress; and (iii) the spor e viability threshold does not exceed 45 degreesC; i.e., the spores are mor e heat-resistant than the mycelium, but they are less heat-resistant than t he spores that are in the state of endogenous dormancy. According to the cu rrent classification of the types of cell metabolism arrest, the exogenous. dormancy of A. niger conidia resembles the pattern of metabolism character istic of vegetative cells during the idiophase.