Imaging and functional characterization of crop root systems using spectroscopic electrical impedance measurements

Maximilian Weigand,Andreas Kemna

doi:10.1007/s11104-018-3867-3

Abstract

Background and aimsNon- or minimally invasive methods are urgently needed to characterize and monitor crop root systems to foster progress in phenotyping and general system understanding. Electrical methods have come into focus due to their unique sensitivity to various structural and functional root characteristics. The aim of this study is to highlight imaging capabilities of these methods with regard to crop root systems and to investigate changes in electrical signals caused by physiological reactions.MethodsSpectral electrical impedance tomography (sEIT) and electrical impedance spectroscopy (EIS) were used in three laboratory experiments to characterize oilseed root systems embedded in nutrient solution. Two experiments imaged the root extension with sEIT, including one experiment monitoring a nutrient stress situation. In the third experiment electrical signatures were observed over the diurnal cycle using EIS.ResultsRoot system extension was imaged using sEIT under static conditions. During continuous nutrient deprivation, electrical polarization signals decreased steadily. Systematic changes were observed over the diurnal cycle, indicating further sensitivity to associated physiological processes. Spectral parameters suggest polarization processes at the μm scale.ConclusionsElectrical imaging methods are able to non-invasively characterize crop root systems in controlled laboratory conditions, thereby offering links to root structure and function. The methods have the potential to be upscaled to the field scale.

Highlights

Root systems play a key role in all kinds of ecosystems and are an essential part in the human food production chain (e.g., White et al 2013, and references therein)
The three experiments presented in this study demonstrate that Spectral electrical impedance tomography (sEIT) and electrical impedance spectroscopy (EIS) are capable of capturing changes in electrical parameters caused by internal physiological processes within crop root systems
We used spectral electrical impedance tomography to image crop root systems in aqueous solutions based on their polarization response, as well as high-speed electrical spectroscopic measurements to observe systematic changes over the diurnal cycle of a plant-root system

Summary

Introduction

Root systems play a key role in all kinds of ecosystems and are an essential part in the human food production chain (e.g., White et al 2013, and references therein). Various characterization methods have been proposed at the laboratory scale (for recent overviews, see Mancuso 2012; Roose et al 2016; Liu et al 2017) Standing out among these are the ComputedTomography (CT) technique (e.g., Gregory et al 2003; Metzner et al 2015) and the Nuclear Magnetic Resonance/Magnetic Resonance Imaging (NMR/MRI) techniques (e.g., Bacicand Ratkovic 1987; Metzner et al 2015), which are actively used to infer structural and physiological information on the rhizosphere. Neutron radiography has been successfully used to image live root segments and their surrounding environment (e.g., Moradi et al 2009; Carminati et al 2010) These methods are still limited to small sample sizes and laboratory conditions (e.g., Thomas et al 2016), and are subject to high application costs. The aim of this study is to highlight imaging capabilities of these methods with regard to crop root systems and to investigate changes in electrical signals caused by physiological reactions

Objectives

Methods

Results

Discussion

Conclusion