Relationship of Cell Transmembrane Electropotential to Potassium and Sodium Accumulation Ratios in Oat and Pea Seedlings

Abstract

Root, stem, and coleoptile tissues were excised from etiolated Pisum sativum variety Alaska and Avena sativa variety Victory seedlings and were allowed to approach equilibrium with Na and K in dilute and concentrated nutrient solutions which also contained Ca and other major inorganic ions. Potential differences from -71 to -123 mv were measured with micro-electrodes between the vacuoles of individual cells and the external solutions. Vacuolar Na and K concentrations were estimated by flame photometry. After applying the Nernst equation to these data, it was suggested that Na was extruded actively from root cells which were in either dilute or concentrated solutions. K appeared to be accumulated actively from dilute external solutions and extruded actively into concentrated solutions.