Photo‐inhibition of Sporulation in Alternaria Solani

Lukens, R. J. (Connecticut Agric. Expt. Sta., New Haven.) Photo‐inhibition of sporulation in Alternaria solani. Amer. Jour. Bot. 50(7): 720–724. Illus. 1963.—Day‐old conidiophores from starved cultures of Alternaria solani require a 12‐hr dark period to produce conidia. If the cultures are illuminated during the dark period, conidial production is inhibited. The action spectrum of light inhibiting conidial formation contains 2 maxima, a sharp one at 450 mμ and a broad one extending from 375 to 425 mμ. The entire action spectrum corresponds approximately to the absorption spectra of riboflavin‐5‐phosphate mononucleotide (FMN) and of 6‐carotene. FMN nullifies the effect of light in inhibiting sporulation, but b‐carotene does not. Flavins appear to be essential for conidial formation and are photo‐inactivated. It is likely that flavins are photo‐receptors through which light inhibits conidial formation in A. solani.