Potassium Flux Studies in Intact Portions of the Roots of Oryza sativa

Abstract

Methods have been developed for studying ion kinetics in a portion of an intact root in its normal growth medium. Based on a simplified mathematical model, the amounts of a substance in the tissue compartments and the unidirectional fluxes between them and to and from the external medium and the xylem can be determined. The methods are applied in an electrochemical analysis of the stte of potassium in a portion of the root of an intact rice seedling. Potassium is shown to be pumped inwardly at the root's surface and to the xylem. There is also an indication that potassium may be actively exported from the vacuoles of cells in very young roots. 86Rb is shown to be suitable as a tracer for potassium in transport studies in rice but not for accumulation to cellular vacuoles.