The Initial Uptake of Ions by Barley Roots: I. UPTAKE OF ANIONS

Abstract

Experiments have been carried out to examine the applicability of the Goüy–Chapman electrical double-layer theory to the initial entry of anions into excised barley roots. An attempt was made to separate the total quantity of labelled iodide or sulphate ions which had entered the roots under varying conditions into three fractions: the two fractions which could be successively eluted with water and extracted with an exchanging solution and that which remained in the roots after these treatments. Except at a low temperature and a low hydrion concentration, the three fractions could not clearly be distinguished, and there were indications of the presence of metabolically maintained positive sites. However, the effect of varying pH on the rate at which anions were eluted with water was consistent with the presence in the roots of a system of pores, the walls of which carried a varying number of negative charges depending on the hydrion concentration. The effect of calcium ions on the magnitude of the water extractable fraction also accorded qualitatively with the double-layer theory.