Ion Fluxes and Phytochrome Protons in Mung Bean Hypocotyl Segments: II. Fluxes of Chloride, Protons, and Orthophosphate in Apical and Subhook Segments.

The active form of phytochrome (Pfr) decreased CI(-) uptake by subhypocotyl hook segments of Phaseolus aureus Roxb. and increased uptake by apical segments. Pfr had similar effects on Pi [(32)Pi] uptake. Modulations of Pi [(32)Pi] uptake were detectable 10 minutes 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 two regions of the hypocotyl are discussed with respect to Pfr-mediated changes in growth and development.