Transpiration and the Selective Uptake of Potassium by Barley Seedlings (Hordeum Vulgare Cv. Bolivia)

Abstract

Selective potassium uptake by barley seedlings decreases with increased solution concentrations above 20 m-equiv /1. This decrease is shown to be due to an action of transpiration. Total uptake of potassium and sodium was unaffected by transpiration, but increased transpiration rate increased sodium uptake and decreased potassium uptake. These changes in sodium and potassium content are difficult to explain in terms of "passive" metabolic components of uptake. It is suggested that sodium and potassium uptake to the shoot is controlled by active anion transport and that water flux acts on movement of sodium and potassium through the root to the site of active transport.