Measuring root properties, the “hidden half” of the plant, is challenging due to their heterogeneous and dynamic nature. A promising method for noninvasive mapping of roots and their activity, spectral induced polarization (SIP), has been introduced. However, measurements of root properties together with their SIP responses are missing, limiting the interpretation of a root's SIP signature. In this study, we coupled SIP measurements of roots in hydroponic solution with measurements of root biomass, surface area, and diameter. Furthermore, we monitored the SIP response of roots poisoned by cyanide, which results in depolarization of the root's cell membrane potential. We found a linear correlation between root biomass and surface area, and the low-frequency electrical polarization. In addition, we demonstrate the relationship between root cell membrane potential and root polarization. Based on the results, we suggest that in comparison with the stem-based approach used by other researchers, the polarization in the contact-free method used in this study is related to the external surface area of the root and external architectural structures such as root diameter and root hair. Overall, a direct link between root properties and their electrical signature was established.
Bibliographical noteFunding Information:
We thank the Ministry of Aliyah and Integration for generous support through a PhD scholarship awarded to K.T. We would also like to thank Z. Peleg for advising about wheat growth. Constructive comments of reviews from Maximilian Weigand and two anonymous reviewers are greatly appreciated. We also thank the associate editor, Andrew Binley, for the prompt processing of this paper.
© 2020 The Authors. Vadose Zone Journal published by Wiley Periodicals, Inc. on behalf of Soil Science Society of America