Close coupling between extrusion of H+and uptake of K+by barley roots

✍ Scribed by Rudolf Behl; Klaus Raschke

• Publisher: Springer-Verlag
• Year: 1987
• Tongue: English
• Weight: 635 KB
• Volume: 172
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00393871

✦ Synopsis

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 I rain. 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 gmoldm-3. Half-maximum rates of net K + uptake and H + extrusion were reached at a K + concentration of about 10 gmol. dm-3. With (slowly absorbable) sulfate as the only anion present, the stoichiometry between H + release and net K + uptake was one. In conclusion, the uptake of K + across the plasmalemma of the ceils of the root cortex is electrically coupled to H + extrusion.