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

The effect of red light on gibberellin uptake by Nicotiana glutinosa L. protoplasts was determined. Five minutes of red light caused over a 50% inhibition of GA3 uptake within 2 minutes. Five minutes of far red light completely reversed the red light effect. The antagonistic effect of far red light indicates that gibberellin uptake is under phytochrome control. The rapid inhibition of gibberellin uptake indicates that phytochrome regulates the permeability properties of the plasma membrane as an initial response and not the intracellular binding of gibberellin.