Plant Morphology: Its Control in Proserpinaca by Photoperiod, Temperature, and Gibberellic Acid.

Growth forms controlled by the photoperiod are modified by temperature and gibberellic acid. Gibberellic acid changes leaf orientation and prostrate growth habit of the short-day plant to that typical of the long-day plant and modifies leaf shape in both types of plants. Low temperature resembles short days in its effect on leaf shape and stem orientation of long-day plants. Geotropic responses of the stem appear to be modified by photoperiod, temperature, and gibberellic acid.