TRANSPORT OF K+ ION AND SELECTIVE TRANSPORT OF ALKALI CATIONS THROUGHPERIDERM AND CUTICULAR MEMBRANES

The transport of KC ion against its concentration gradient through iso lated periderm (PM) and cuticular (PFCM) membranes at different pH and salt concentrations was investigated. The mean transport rate and tra nsport fraction were calculated, and a tentative transport mechanism d ue to fixed charges was proposed. The transport system depends on the concentration gradient of K+ ions and H+ ions and the pH gradient was the main driving force. This system is characterised by asymmetry of b inding on both compartments of the membrane for the formation and diss ociation of carrier carboxyl groups in the membrane matrix. These carr ier groups are dissociated at high pH ranges. The studies were then ex tended to examine the selective transport of alkali cations by using K -Na and K-Li binary systems with various pH gradients. In the transpor t of metal ions, the selectivity depends on both the hydrated ionic si ze and the interaction between the carboxyl groups in the membrane and the metal ions.