Sporulation in Rhizopus sexualis and Some Other Fungi Following a Period of Intense Respiration

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Abstract
Rhizopus sexualis grown at 20° C. on liquid I per cent. malt or glucose-asparagine medium showed a peak of respiratory activity between 40 and 55 hours-after inoculation. Rate of respiration then fell until it reached a steady low level which coincided with maximum mycelial growth. Zygospore initiation occurred at or just after the peak of respiration. At a low temperature (9° C.) or with high concentrations of glucose the respiration peak was less marked and no zygospores developed. Single ‘plus’ or ‘minus’ strains of the heterothallic species Mucor hiemalis and Phycomyces blakesleeanus showed a pattern of respiration and mycelial growth similar to that of R. sexualis but no zygospores were formed. Zygospores did not develop without a preliminary period of intense respiration, but such a peak period could occur without being followed by zygospore formation. A strain of Sordaria fimicola was grown at 25° C. on a synthetic medium with 5.0 per cent. sucrose or glucose as source of carbon. Respiration reached a peak at approximately 4 and 5 days respectively, the actual peak value being twice as large on sucrose as on glucose. Dry weight of mycelium was greater on glucose than on sucrose. Perithecia were formed only on the sucrose medium. Visible peri-thecial initials were first seen shortly after the occurrence of the respiratory peak. Mature perithecia were present 3 days later. The possible significance of these results is discussed.