## 3 Results and Discussion  
### Electrical Model of the Branch Section  
In some models, a constant phase element (CPE) is considered [23] to obtain more correct EIS data as well as differentiate resistive and capacitive elements in the structure of biological tissue. The CPE remains unchanged throughout the frequency range under consideration [24], which helps to smooth out some inhomogeneities in the electrical properties of tissues and reduce the complexity of their biological responses when using EIS [11; 12]. Accordingly, the electrical properties of these tissues vary significantly depending on the parametric composition and distribution of cells and cell fluid. The liquid inside and outside the cell consists of water and electrolytes dissolved in it (salt, etc.). Therefore, it is characterized by a resistive electrical state. At the same time, the cell membrane is a lipid bilayer surrounding the cytoplasm, so it has capacitive properties [13]. EIS makes it possible to study some properties of cells by using variable electrical signals of different frequencies and then measuring the output electrical parameters in terms of current or voltage. In our case, the impedance refers to the frequency-dependent ratio of the voltage signal to the current signal called the impedance. The impedance can be expressed both in rectangular coordinates (1) and in polar coordinates (2). \[Z=R+jX, \tag{1}\] \[Z=|Z|e^{j\varphi}\Bigg{\{} \begin{array}{l}|Z|=\frac{|\varphi(t)|}{| i(t)|},\\ \varphi=2\pi f\Delta t;\end{array}  \tag{2}\]  
where \(R\) is the active resistive component, \(jX\) is the reactance, \(|Z|\) is the impedance modulus, \(\varphi\) is the phase, \(|\,\,\,v(t)|\) is the voltage signal, and \(\,\,\,i(t)|\) is the current signal. The module is found as the ratio of the voltage signal to the current signal, and the phase is calculated by the shift between these signals. In a simplified form, the resistance of a part of the tree is represented as:  
\[R=\rho\frac{l}{S}, \tag{3}\]  
where \(\rho\) is the resistivity of the tree, \(l\) is the distance between electrodes, and \(s\) is the cross-sectional area of the plant stem. For qualitatively recording the grafted pear tree condition, a pair of electrodes were fixed above and below the grafting site (see Section 2 and Figure 3). A voltage with a certain amplitude was applied to the electrodes, and then the imaginary and real components of the current were measured and the electrical impedance was inferred. When measuring the voltage, it is necessary to take into account the polarization of the electrodes associated with diffusion, partial electrolysis at the sites of electrode fixing, the appearance of parasitic capacitive resistances, and a transient voltage drop, which was also observed. To eliminate the inaccuracies, the measurements were carried out several times with the current frequency change in the range of 4 kHz-100 kHz. To obtain comparable results, the measurements were carried at different distances from the electrodes (100-300 mm stepping 100 mm; Figure 4). Thus, we tested the validity of Equation (3) regarding the dependence on the length of the measured section of the plant. The use of EIS in a wide frequency range allows working in the range corresponding to the end of the \(\alpha\)-dispersion and a wide range of \(\beta\)-dispersion. As a result, we find biompedance differences in plant tissue samples. When a low-frequency current is applied to a plant, the surface components of its tissue are polarized, being essentially capacitive components. It impedes passage of the electric current through them, so the current largely flows through the extracellular fluid. At higher frequencies, the capacitive resistance, as well as the resistance in the surface tissues of the plant, declines [13; 14]. The obtained data of the correlation of the impedance modulus on the length of the measured part of the tree indicate the applicability of Equation (3) to our case, with the exception of small deviations in the results obtained at frequencies 2 and 3 kHz.