Toward noninvasive monitoring of plant leaf water content by electrical impedance spectroscopy

•A cost-effective, four-electrode electrical impedance analyzer has been built and tested.•The use of CPEs in the impedance equivalent circuit of plant tissues improves data fitting.•Noninvasive electrodes placed on leaf samples yield useful information about plant leaf water content.•Water loss is best tracked by the resistance modelling extracellular fluid. Plant water content is one key factor that affects the wellbeing of plants. Furthermore, detecting plant water needs in a timely manner is important when considering irrigation strategies (water management). A first step toward plant water monitoring is the availability of a portable and cost-effective system that yields reliable information. Electrical impedance spectroscopy (EIS) has previously been used invasively to provide such data and can be implemented at an acceptable cost. In this work, a cost-effective impedance analyzer capable of performing noninvasive four-electrode measurements was built. In addition, data fitting has been improved by using a modified equivalent circuit model, yielding relevant information about the plant water status. The results show that the resistor that models the extracellular fluid can track the change in the water content of a plant leaf while it is drying at room temperature. On the other hand, impedance data might provide information about the leaf tissue structure at small interelectrode distances.