Dark red kidney beans were grown in complete darkness, except for brief exposures to red radiant energy. Internodes did not elongate appreciably until the elongation of the preceding internode was nearly completed. Since hypocotyl elongation is inhibited by exposure to red radiant energy, elongation of the first internode of red-irradiated plants begins earlier than that of dark-grown ones. 2. When total stem length is used as a measure of the response to gibberellin, there is an apparent interaction between the chemical and the photoreaction. This interaction, however, is not real but is a result of the light-induced elongation of other internodes. Thus, the red-irradiated plants have a greater number of internodes upon which the gibberellin can act. There is no apparent interaction between the reaction to gibberellin and the photoreaction whenever a single internode is used as a measure of the response. 3. The action of AMO-1618 appears to be interrelated with the action of gibberellin, but not with the photoreaction. The retardation induced by AMO-1618 is equally great on red-irradiated and darkgrown plants.
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Downs et al. (1960) studied this question.