Pikul Wanichapichart, Kanokkarn Maswiwat, and Kamnoon Kanchanapoom

pp. 799 - 806

Abstract

This work reports elongation of Dendrobium protoplasts in an ac electric field between two cylindrical electrodes. A protoplast firstly was translated towards an electrode by dielectrophoretic force in 17
kV.m^-1 field strength at 1 MHz, and secondly it was elongated due to an interaction between an induced
electric dipole (µ) and the electric field (E). Protoplast elongation was observed by varying both the field
strength at 30, 45, 60, and 85 kV.m^-1 and field frequency at 0.5, 1, 5, and 10 MHz. For a given field
frequency and field strength, a parameter a/b (major/minor axis) was measured as the protoplast elongation. Two-step elongation and restoration phases were observed. The former was completed within 2 minutes of field exposure, and the latter was completed within 15 seconds regardless of the field exposure time
between 3 and 20 minutes. The evidence of a complete restoration indicated that the elasticity of the protoplast membrane obeyed Hooke’s law. This study also found that elastic constant k of the membrane varied
non-linearly with the field strength. It was found to be from 0.04 to 0.08 mN.m^-1, dependent on the field
frequency