Phytochrome and endogenous gibberellin-like substances in etiolated and irradiated oat seedlings

Abstract

The level of gibberellin-like substances was investigated in oat coleoptiles with different stationary states of phytochrome and in leaf segments which had been etiolated and irradiated with red light. Etiolated coleoptiles and leaves containing maximum amounts of the PR form of phytochrome were characterized by an increased level of bound gibberellins. Irradiation with red light resulting in the photoconversion of phytochrome into the Pt R form caused the appearance of a high content of free gibberellins. It seems that the releasing the hormones from bound forms correlated with the formation of phytochrome PFR may be an important aspect of the mechanism of phytochrome action in the processes of seedling deetiolation. The interrelation between phytochrome and plant hormones in the control of photomorphogenesis of young monocotyledonous seedlings is also discussed.