On the Interpretation of Four Point Impedance Spectroscopy of Plant Dehydration Monitoring

In this paper, we present a study of in-vivo four-point impedance spectroscopy (FPIS) for plant monitoring. FPIS was measured vs. time under hydration/dehydration cycles in tobacco plants. The plants were set up in a gravimetric system and grown in sand for better control of water drainage. Data was gathered at fixed time intervals, every few minutes, collecting the complex impedance values at a few hundred frequencies in the 40 Hz to 2MHz range. Due to the large amount of the collected data, the issues of data representation and interpretation became a challenge. These two issues are discussed examining system orientated approaches, along with possible methods representing and interpreting the data. The results of the electrical measurements and the various analysis methods were compared to those of the well-established agriculture gravimetry measurements. The FPIS results show that the impedance depends on the plant status, similar to the value expressed in the gravimetry system, thus the plant status can be interpreted from the electrical measurements. Each of the data interpretation methods examines the change and is suggested for further device development.