Electrophoresis, Zeta potential and Surface Charges of Barley Mesophyll Protoplasts

The electrophoretic mobility of barley mesophyll protoplasts was measured by the micro-electrophoresis technique to determine the surface charge density in medium that contained various cations and anions at neutral pH. The surface charge was strongly influenced by the presence of di- and trivalent cations in the medium, suggesting that certain di- and trivalent cations are specifically adsorbed on or bound to the plasma membrane of the protoplasts. The order of ad-sorbability was Mg2+ < Ca2+, Mn2+, Ba2+ for divalent cations, and La3+ < < Sm3+ < Tm3+, Yb3+ for trivalent cations. The adsorption of Ca2+ and La3+ ions on the surface of the membrane was analyzed using the Langmuir adsorption isotherm. The maximum amount of adsorption and the adsorption coefficient were found to be 3.17 mC/m2 and 1.16 mM−1 for Ca2+ ions, and 7.12 mC/m2 and 8.26 mM−1 for La3+ ions, respectively.