Application of impedance spectroscopy for selecting frost hardy varieties of English ryegrass

Abstract

The frost hardening and frost damage of 12 varieties of English ryegrass (Lolium perenne) was studied by electrical impedance spectroscopy. For the measurement of the impedance spectrum (80 Hz to 1 MHz) a 10 mm length sample was cut from the stem above the growing point, but the growing point was included. The impedance spectra were analysed by an asymmetric distributed circuit model. The impedance spectra were measured at two phases of hardiness and after freezing, i.e. (a) before hardening, (b) after hardening in controlled conditions, and (c) after controlled frost exposure at -16 °C after hardening. Two model parameters, i.e. intra- and extracellular resistance, increased with hardening. The intracellular resistance and the skewness factor before hardening, and the ratio between those two parameters before and after hardening, strongly correlated with hardening of different varieties of English ryegrass. The extracellular resistance and the relaxation time decreased as a result of the frost exposure at -16 °C.