Electrical imaging of plant root zone: A review

Imaging of the root zone of a plant is extremely important for studies of the root growth and development, root moisture and nutrient absorption, and water and nutrient transport in the root zone. Many noninvasive methods have been proposed for mapping, characterization or monitoring of the generally invisible and complex root zone. Benefiting significantly from its suitability for low-cost and portable device implementation, its applicability at various scales and its ability to characterize physiological functions, electrical imaging is a very promising method for use in root zone applications. Over the last twenty years, increasing numbers of electrical imaging studies have been performed on measurement of the roots or the root zone moisture. However, electrical imaging of the root zone poses many technical challenges, not only in terms of the measurements but also in the image reconstruction computations. This paper will systematically review the progress, advantages and limitations of the related research, along with the technical aspects, which include the measurement principles and the electrical properties of the root zone, modeling and inversion, inversion software, uncertainty, resolution, and parallel computing. Overall, we believe that electrical imaging will have a brighter future for root zone applications in the coming decade.