Membrane ATPase Activity of Barley Roots and Potassium Uptake by Isolated Stele and Cortex

Abstract

AbstractUptake of potassium ions by isolated stelar tissues of barley from 0.5 and 10 mM K+ was respectively 13 and 3.6% of that of the cortical tissues. 0.1 mM H2PO4, LO mM ATP and 10 mM Ca(NO3)2 did not increase the potassium uptake of either stele or cortex during 5 h of uptake period.A time‐course incubation for histological demonstration of the ATPase activity of the plasmalemma and tonoplast of the matured sections of the roots demonstrated a greater activity for the cortical than the stelar tissue. In the stelar parenchyma cells, the plasma lemma showed a higher activity than the tonoplast. These results, which support the “leakiness hypothesis” of the stele, are discussed in relation to the proposed mechanisms of radial ion transport in roots.