Carbon-dioxide inhibits phorogenesis in phycomyces and blue-light overcomes this inhibition

Carbon dioxide inhibits phorogenesis in Phycomyces as does a gas produced by Phycomyces. We have isolated mutants which are supersensitive (B451, B452) or resistant (B455, B457) to the gas. These mutants are also supersensitive or resistant to CO2. We conclude that the gas is CO2. A pulse of blue, but not red, light overcomes this inhibition. The CO2 sensitive step is completed 5–10 h before the appearance of visible sporangiophore initials.