PHYTOCHROME AND GROWTH-SUBSTANCES IN THE CONTROL OF OAT SEEDLINGS ELONGATION

Short red light irradiation which stimulated the elongation of isolated oat coleoptiles also caused an increase in both auxin and gallic acid-like compound content in them. The effect of red light was partly reduced by far-red light irradiation. Prolonged white light illumination which induced growth inhibition in intact oat seedlings caused at the same time a decrease in the content of auxin and very pronounced increase in the amount of gallic acid. There were not any detectable changes of the content of abscisic acid in the seedlings. Phytochrome-controlled changes in the endogenous level of gallic acid-like compound are not in direct relationship with the regulation of the growth of oat coleoptiles and seedlings by light. The mechanism of action of light in the elongation of coleoptiles and seedlings seems to be causatively connected with the regulation of IAA content in irradiated tissues.