Factors affecting electrical impedance of internodal stem sections

A sample holder was designed and built to facilitate measuring the magnitude and phase angle of the electrical impedance of internodal stem sections from Cornus stolonifera Michx. A nonpolarizing, electrically conducting manganese dioxidecarbon paste used between the stem sample and the electrodes of the sample holder allowed measurement of impedance at frequencies from 50 hertz to 500 kilohertz without electrode polarization or electrical interference. The impedance magnitude was linearly dependent on the sample length, but this dependence was minimized by computing a normalized impedance magnitude. The normalized impedance magnitude (Z(nf)) was calculated using the impedance magnitude (Z) at any specified frequency (f) and the impedance magnitude at 500 kilohertz (Z(500 khz)) in the following formula: Z(nf) = (Z - Z(500 khz))/Z(500 khz). The normalized impedance magnitude was sensitive to injury produced by boiling and peeling the sample. Electrical impedance measurements on the bark and wood separately demonstrated that they have different electrical properties.