Electrokinetic parameters of ion transport across isolated pepper cuticular membranes

The transport of NaCl and CaCl2 solutions across isolated pepper cuticular membranes was studied by means of conductivity, membrane potential and diffusion experiments. Some characteristic membrane parameters such as the electrical resistance, ionic and salt permeabilities were obtained as a function of the electrolyte concentrations. Cuticle morphological asymmetry accounts for differences in membrane potential values under external reverse gradients. The influence of temperature on the membrane structure was also considered, but only small changes in the electrokinetic parameters were obtained. From the NaCl diffusion experiments two activation energies were determined (54.8 kJ/mol for temperature ranging between 15 and 35 degrees C, and 20.6 kJ/mol for the interval of temperature between 40 and 60 degrees C), which could be associated to thermal transitions in the molecular structure of the cuticle for the interval 30-40 degrees C. (C) 1998 Elsevier Science B.V.