Sodium Fluxes, Xylem Transport of Sodium, and K/Na Selectivity in Roots of Seedlings of Hordeum vulgare, cv California Mariout and H.distichon, cv.Villa.

Abstract

Summary Sodium fluxes were measured by compartmental analysis in roots of intact seedlings of Hordeum vulgare , cv.California Mariout and H distichon , cv.Villa in the concentration range 0.1 to 50 mol m -3 Na + .Apart from xylem transport all sodium fluxes and the cytoplasmic and vacuolar sodium content were higher in Villa than in Mariout, which is known for its high salt tolerance.This was also true for K + -dependent Na + extrusion (KINa exchange) across the plasmalemma, indicating that a higher degree of KINa selectivity at the plasmalemma is not per se decisive for salt tolerance in barley.At high external concentrations xylem transport of Na + was substantially higher in Mariout than in Villa.For both barley species root to shoot sodium transport was almost independent of external concentration between 10 and 50 mol m -3 NaCl and thus appears to be tightly controlled.