Review on the Application of Bioimpedance Methods in Plant Root Biology Research

Due to the limitation of appropriate methods, the vast majority of research on plant traits has concentrated on above-ground tissues rather than root systems hindered by soil. Conventional root investigation methods such as soil cores, monoliths, and in-growth cores are inherently labour intensive, time-consuming and destructive. There is, therefore, an urgent need for a non-destructive but reliable method for the estimation of the structure and function of root systems in situ. Numerous studies have shown good correlations between electrical impedance parameters (capacitance, resistance and electrical impedance spectroscopy) and root weight and morphology with the measurement of roots under an external electric field. Recently, however, other researchers have argued that the understanding of the electrical behaviour of roots is still poor. This paper introduces the basic theory and measurement of bioimpedance, reviews the different outcomes of root research using bioimpedance, and suggests several questions in regard to the application of bioimpedance. The current research will provide a reference for studies examining non-destructive root systems in situ.