Inductive Control of Indoleacetic Acid Oxidase Activity by Red and Near Infrared Light.

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Abstract
The IAA oxidase activity of buds of etiolated peas, as assayed in extracts with the addition of 2,4-dichlorophenol or manga-nous ion, was greatly inhibited by 2 to 750 kiloergs/cm2 red light given to the intact plants during a brief period at some time before harvest. Maximum inhibition with a given energy was obtained by illuminating about 16 hours before harvest. The inhibition was reversible by near infrared radiation given immediately after the red light, but not more than 1 hour afterwards. The activities of extracts from dark-grown and red-illuminated buds could be made the same by dilution, or by dialysis, suggesting that the inhibition may be due entirely to increased levels of a dialyzable inhibitor. The IAA oxidase activity of young internode tissue was insensitive to the low energies used. The results may be of significance in the physiology of de-etiolation and of other processes controlled by red and near infrared radiations.