Detection Of Physiological Parameters Of Epipremnum Aureum Leaves Based On Electrical Impedance Spectroscopy

The rapid detection of leaf physiological parameters is the key to the rapid development of intelligent flowerpot technology.The existing detection methods have the problems of damaging leaves or expensive equipments.As an economical and convenient rapid detection method,electrical impedance spectroscopy(EIS)has been widely used in the field of plant physiological parameters detection.In order to detect leaf moisture content conveniently and non-destructively and study the feasibility of detecting leaf photosynthetic parameters based on EIS,the leaf impedance of epiremnum aureum was measured under different leaf moisture content and photosynthetic parameters,and the EIS was fitted with the equivalent circuit model,Then,the prediction model of the leaf moisture content and photosynthetic parameters of epipremnum aureum based on electrical characteristic parameters was established.The main results are as follows:(1)A non-destructive measurement method based on ECG gel of the leaf impedance named indirect contact method was proposed,and the optimal measurement conditions of the epiremnum aureum leaf impedance were determined.In the frequency range of 100 Hz～1 MHz,the relative standard deviation of the inverted three leaf impedance in the epiremnum aureum stem measured by this non-destructive method was less than 6%,when the measuring electrodes were symmetrically arranged on both sides of the leaf vein,and the front middle area closing to the petiole of the leaf was measured.(2)The impedance characteristics of the ECG gel and its influence on leaf impedance measurement was clarified,and an indirect contact equivalent circuit model based on ECG gel was established.ECG gel has the characteristics of resistance capacitance composite,and its contact with the leaf surface is the main reason for the two semicircular arcs in the measured Cole-Cole plot;When the established indirect contact equivalent circuit model is used to fit the EIS of the epiremnum aureum leaf measured by the non-destructive measurement method based on ECG gel,the fitting determination coefficients of the real and imaginary part of the impedance are higher than 0.999,the relative errors of the parameter values indicating the leaf structure of the equivalent circuit model are all less than51%compared with the results of common measurement methods.(3)The prediction model of the leaf moisture content of epiremnum aureum based on electrical characteristic parameters was established.with the decrease of leaf moisture content,the leaf impedance modulus at the same frequency decreases,the arc radius of high-frequency section of Cole-Cole plot decreases,and the curve of low-frequency section shifts to the left and lower;In the range of 72%-91%of the leaf moisture content,the impedance modulus at 10 k Hz and 16 k Hz and the phase angle at 25 k Hz and 40 k Hz have good correlation with the leaf moisture content.The above frequencies are the sensitive frequencies for predicting leaf moisture content of epipremnum aureum;The multivariate linear regression model based on impedance original data has the best prediction effect among the prediction models of the epipremnum aureum leaf moisture content established by simple and multivariate linear regression and BP neural network,its R~2is 0.812 and RMSE is 0.021.(4)Based on electrical characteristic parameters,prediction models of photosynthetic parameters of the epipremnum aureum leaf under light intensity stress were established.The best prediction models of leaf net photosynthetic rate,stomatal conductance and transpiration rate of the epipremnum aureum were exponential function models based on the impedance modulus at 250 Hz,respectively with R~2of 0.819,0.838 and 0.792,and RMSE of 0.340,1.067 and 0.028.