Effect of Phytochrome on the Uptake of Gibberellin by Protoplasts of Nicotiana glutinosa L.

The effect of red light on gibberellin uptake by Nicotiana glutinosaL. protoplasts was determined. Five minutes of red light causedover a 50% inhibition of GA₃ uptake within 2 minutes. Five minutesof far red light completely reversed the red light effect. Theantagonistic effect of far red light indicates that gibberellinuptake is under phytochrome control. The rapid inhibition of gibberellin uptake indicates that phytochromeregulates the permeability properties of the plasma membraneas an initial response and not the intracellular binding ofgibberellin. ¹Department of Plant Pathology, University of Missouri. (Received October 28, 1985; Accepted April 23, 1986)