Complexity of potassium acquisition: How much flows through channels?

Abstract

The involvement of potassium (K+)-selective, Shaker-type channels, particularly aKt1, in primary K+ acquisition in roots of higher plants has long been of interest, particularly in the context of low-affinity K+ uptake, at high K+ concentrations, as well as uptake from low-K+ media under ammonium (NH4+) stress. We recently demonstrated that K+ channels cannot mediate K+ acquisition in roots of intact barley (Hordeum vulgare L.) seedlings at low (22.5 μm) external K+ concentrations ([K+]ext) and in the presence of high (10 mm) external NH4+, while the model species Arabidopsis thaliana L. utilizes channels under comparable conditions. however, when external NH4+ was suddenly withdrawn, a thermodynamic shift to passive (channel-mediated) K+ influx was observed in barley and both species demonstrated immediate and dramatic stimulations in K+ influx, illustrating a hitherto unexplored magnitude and rapidity of K+-uptake capacity and plasticity. here, we expand on our previous work by offering further characterization of channel-mediated K+ fluxes in intact barley, with particular focus on anion effects, root respiration and pharmacological sensitivity and highlight key additions to the current model of K+ acquisition. © 2013 Landes Bioscience.