Phytochrome and potassium uptake by mung bean hypocotyl sections.

Uptake of potassium (K) and (86)rubidiumlabelled potassium ((86)Rb) by sub-hypocotyl hook sections of Phaseolus aureus L. was inhibited by red light. The effect was reversible with far red light. Using short exposures of high irradiance the effect on (86)Rb-labelled K uptake was observed after 5 min. The response showed no specificity for a particular anion. Uptake of (86)Rb-labelled K by sections cut immediately below the cotyledons was enhanced by red light after 10 min incubation and was also far red reversible. These results are interpreted as a rapid phytochrome-induced change in membrane properties resulting in modified K uptake.