Phytochrome Control of Maize Coleoptile Section Elongation : A RAPID LOSS OF PHOTOREVERSIBILITY.

A rapid loss of far red light (FR) reversibility of red-light (R) stimulated elongation of maize coleoptile sections was observed. Reversal was not possible when the interval between R and FR treatment was greater than 45 seconds. Most of the R-stimulated elongation occurred during the first 15 hours after irradiation.Exogenous gibberellic acid did not alter the time course of R/FR reversibility loss. These results are interpreted as indicating independence of R- and gibberellic acid-stimulated elongation in this system.