Close coupling between extrusion of H+ and uptake of K+ by barley roots |
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Authors: | Rudolf Behl Klaus Raschke |
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Affiliation: | (1) Pflanzenphysiologisches Institut und Botanischer Garten, Untere Karspüle 2, D-3400 Göttingen, Federal Republic of Germany |
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Abstract: | Extrusion of H+ by intact barley (Hordeum vulgare L.) roots was automatically titrated. Simultaneously, uptake of K+ into the roots, transport of K+ through the roots, and (as a residual term) accumulation of K+ within the root tissue were determined. When no monovalent cation was present in the medium the steady rate of H+ release was close to zero. Addition of K+ stimulated H+ extrusion within less than 1 min. The stimulation of H+ release was apparently limited only by the movement of K+ through the apoplast of the roots. The steady rate of H+ extrusion depended on the availability of external K+ and saturated at a K+ concentration of about 100 mol· dm-3. Half-maximum rates of net K+ uptake and H+ extrusion were reached at a K+ concentration of about 10 mol·dm-3. With (slowly absorbable) sulfate as the only anion present, the stoichoimetry between H+ release and net K+ uptake was one. In conclusion, the uptake of K+ across the plasmalemma of the cells of the root cortex is electrically coupled to H+ extrusion. |
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Keywords: | Hordeum (roots) Plasmalemma Potassium (uptake, accumulation, transport) Proton extrusion Root (K+ uptake, H+ extrusion) |
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