The physiological relevance of Na+-coupled K+-transport

• Published in: Plant physiology (Bethesda) Vol. 112; no. 4; pp. 1609 - 1616
• Main Authors: Maathuis, F.J.M. (Univ. of York, UK.), Verlin, D, Smith, F.A, Sanders, D, Fernandez, J.A, Walker, N.A
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01-12-1996
• Subjects: Barley; Bioenergetics; Biological and medical sciences; CATION; CATIONES; Cell physiology; Depolarization; Electrodes; ENERGIA; ENERGIE; Fundamental and applied biological sciences. Psychology; ION; IONES; Membrane potential; Plant cells; Plant growth; Plant physiology and development; Plant roots; PLANTAS; PLANTAS ACUATICAS; PLANTE; PLANTE AQUATIQUE; Plants; Plasma membrane and permeation; POTASIO; POTASSIUM; SODIO; SODIUM; Monocotyledones; Zea mays; Root; Electrophysiology; Ion transport; Bryophyta; Hydrocharitaceae; Inorganic element; Hepaticae; Cereal crop; Arabidopsis thaliana; Sodium; Cruciferae; Gramineae; Dicotyledones; Electrochemical gradient; Angiospermae; Spermatophyta; Aquatic plant; Experimental plant; Biological accumulation; Potassium; Triticum aestivum
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.112.4.1609

Plant roots utilize at least two distinct pathways with high and low affinities to accumulate K+. The system for high-affinity K+ uptake, which takes place against the electrochemical K+ gradient, requires direct energization. Energization of K+ uptake via Na+ coupling has been observed in algae and was recently proposed as a mechanism for K+ uptake in wheat (Triticum aestivum L.). To investigate whether Na+ coupling has general physiological relevance in energizing K+ transport, we screened a number of species, including Arabidopsis thaliana L. Heynh. ecotype Columbia, wheat, and barley (Hordeum vulgare L.), for the presence of Na+-coupled K+ uptake. Rb+-flux analysis and electrophysiological K+-transport assays were performed in the presence and absence of Na+ and provided evidence for a coupling between K+ and Na+ transport in several aquatic species. However, all investigated terrestrial species were able to sustain growth and K+ uptake in the absence of Na+. Furthermore, the addition of Na+ was either without effect or inhibited K+ absorption. The latter characteristic was independent of growth conditions with respect to Na+ status and pH. Our results suggest that in terrestrial species Na+-coupled K+ transport has no or limited physiological relevance, whereas in certain aquatic angiosperms and algae this type of secondary transport energization plays a significant role