Electrical Impedance Spectroscopy of plant cells in aqueous biological buffer solutions and their modelling using a unified electrical equivalent circuit over a wide frequency range: 4Hz to 20 GHz

A simple, ultra-wide frequency range, equivalent circuit for plant cell suspensions is presented. The model incorporates both the interfacial interactions of the suspension with the electrode, dominant at low frequencies, and the molecule and cell polarization mechanisms dominant at higher frequencies. Such model is useful for plant cell characterization allowing a single set of parameters over >9 orders of magnitude, whilst allows electronic simulations over the whole frequency range using a single model, simplifying the design of electronic systems of integrated plant cell sensors. The model has been experimentally validated in the frequency range of 4 Hz–20 GHz with each component in the circuit representing a physical phenomenon. Various cell concentrations (MSK8 tomato cells in Murashige and Skoog media) have been investigated, showing clear correlations of the cell capacitance increasing within the range of 200–600 pF, whilst cell resistance (R) decreasing within the range of approximately 0.8–3 kΩ within the cell concentration X–Y cells/mL range. This is the first model ever reported that covers such a wide frequency range and includes both interfacial and polarization effects in this simple form.