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Auxin carriers in Cucurbita vesicles : I. Imposed perturbations of transmembrane pH and electrical potential gradients characterised by radioactive probes


Planta 171(4): 501-506
Auxin carriers in Cucurbita vesicles : I. Imposed perturbations of transmembrane pH and electrical potential gradients characterised by radioactive probes
The behaviour of radioactive probes of transmembrane pH gradients ([14C]butyric acid) and electrical potential gradients (86Rb+ and S14CN-) has been characterised in membrane vesicles from Cucurbita pepo L. hypocotyls subjected to changing gradients and ionophore-mediated changes in the conductivity of K+ and H+ ions. The vesicles are sealed in the presence of 25 mM KCl. The K+ ionophore valinomycin changes the distribution of 86Rb+ and of S14CN- in opposite directions, which depend on the external K+ concentration. The accumulation of [14C]butyric acid by the vesicles and its association with the membranous phase are enhanced by increasing acidity, as expected for this lipophilic weak acid (pKa = 4.8). Uptake of S14CN- increases and valinomycin-stimulated 86Rb+ uptake decreases when the external pH is lowered, indicting a strongly pH-dependent H+ diffusion potential.


Accession: 001534130

PMID: 24225712

DOI: 10.1007/BF00392298



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