Effect of poly-L-lysine on potassium fluxes in red beet tissue

Poly-L-lysine concentrations (10−6 m) which cause slight leakage of pigment from beet cells completely disrupt the kinetics of*K (labeled) absorption at 25°C in the range 0.01 to 50mm KCl. Lower concentrations of polylysine (10−7 to 10−9 m) interfere with potassium fluxes at both cell membranes, initially increasing efflux across the plasma membrane and decreasing the capacity of the cytoplasm to retain ions during flux experiments at 2°C. At 25°C, these concentrations of polylysine increase*K (labeled) absorption from 0.2mm KCl, but not from 10mm KCl. These responses are discussed in relation to ion transport via the three-compartment in-series model proposed for plant cells. Particular emphasis is placed on the role of the plasma membrane in K transport from solutions of low concentration.