Ion Fluxes and Phytochrome Protons in Mung Bean Hypocotyl Segments

Abstract
The active form of phytochrome (Pfr, far red form) decreased Cl- uptake of subhypocotyl hook segments of P. aureus Roxb. and increased uptake by apical segments. Pfr had similar effects on Pi [32Pi] uptake. Modulations of Pi [32Pi] uptake were detectable 10 min. following photoconversion. Pfr may modulate Pi influx across the plasmalemma. Pfr inhibited H+ extrusion by subhook segments and enhanced extrusion by apical hook segments. No rapid effects on H+ extrusion were found. Phytochrome may regulate a K+-H+ exchange process. The differential responses of the 2 regions of the hypocotyl are discussed with respect to Pfr-mediated changes in growth and development.