Effect of Phytochrome on Uptake and Efflux of Gibberellin

The effect of red light on uptake and efflux of gibberellinby etiolated pea stem sections has been determined by the techniqueof compartmental analysis. Exposure of segments to red lightinhibited uptake and efflux of [³H]-GA₁ by the cytoplasmic compartmentwhile efflux from the vacuolar compartment was not significantlyaffected. It is suggested that phytochrome may alter the permeabilityproperties of the plasma membrane and/or the binding of GA₁,as, a means of controlling the basipetal transport of gibberellin. (Received November 19, 1984; Accepted March 2, 1985)