Non-destructive estimation of leaf moisture content of Epipremnum aureum based on electrical impedance spectroscopy

Electrical impedance spectroscopy (EIS) is a technique used for detection of leaf moisture content (LMC). Generally, EIS is inconvenient and destructive. This paper proposed a non-destructive method for predicting LMC of Epipremnum aureum based on the impedance spectrocopy with the combination of ECG gel and needle electrodes. An effective equivalent circuit model for the corresponding gel contact method was established. The LMC model of E. aureum was obtained based on equivalent circuit parameters. The results demonstrated that there were two arcs in the Cole–Cole plots of the leaves measured by the gel contact method. The arc in the high frequency region reflected the impedance characteristics of the leaf, while the arc in the low frequency region was relevant to the impedance of the ECG gel and the polarization impedance caused by the contact with leaves. The gel contact model was suitable for fitting the leaf impedance spectroscopy measured by the gel contact method. The R_R² and R_X² for each R and X were both greater than 0.999. Meanwhile, the LMC prediction model based on extracellular resistance showed the best performance, with the coefficient of determination (R²) and root-mean-square error (RMSE) for prediction being 0.803, 0.0580, respectively.