Abstract
BackgroundTo face climate change and subsequent rainfall instabilities, crop breeding strategies now include root traits phenotyping. Rapid estimation of root traits in controlled conditions can be achieved by using parallel electrical capacitance and its linear correlation with root dry mass. The aim of the present study was to improve robustness and efficiency of methods based on capacitance and other electrical variables, such as serial/parallel resistance, conductance, impedance or reactance. Using different electrode configurations and stem contact electrodes, we have measured the electrical impedance spectra of wheat plants grown in pots filled with three types of soil.ResultsFor each configuration, parallel capacitance and other linearly independent electrical variables were computed and their quality as root dry mass estimator was evaluated by a ‘sensitivity score’ that we derived from Pearson’s correlation coefficient r and linear regression parameters. The highest sensitivity score was obtained by parallel capacitance at an alternating current frequency of 116 Hz in three-terminal configuration. Using a clamp, instead of a needle, as a stem electrode did not significantly affect the capacitance measurements. Finally, in handheld LCR meter equivalent conditions, capacitance had the highest sensitivity score and determination coefficient (r2 = 0.52) at 10 kHz frequency.ConclusionOur benchmarking of linear correlations between different electrical variables and root dry mass enables to determine more coherent practices for ensuring a sensitive and robust root dry mass estimation, including in handheld LCR meter conditions. This would enhance the value of electrical capacitance as a tool for screening crops in relation with root systems in breeding programs.Electronic supplementary materialThe online version of this article (doi:10.1186/s13007-016-0133-7) contains supplementary material, which is available to authorized users.
Highlights
To face climate change and subsequent rainfall instabilities, crop breeding strategies include root traits phenotyping
Frequency dependence of the parallel capacitance: root dry mass correlation Determination coefficients from linear correlations between root dry mass and parallel capacitance are plotted in Fig. 2 as a function of frequency
The root dry mass (RDM) relation with Cp is: Literature data Data that we could retrieve from prior experiments on the quantification of plant root biomass using electrical capacitance were compiled [18, 19, 22,23,24,25, 32]
Summary
To face climate change and subsequent rainfall instabilities, crop breeding strategies include root traits phenotyping. Rapid estimation of root traits in controlled conditions can be achieved by using parallel electrical capacitance and its linear correlation with root dry mass. Fast imaging techniques [16] and methods based on the root electrical properties could shorten greenhouse selection stages, but at the cost of limited pot size and varying measurement reliability, respectively. It has been argued that the correlation between capacitance and root mass comes from allometric relationships in hydroponics [25, 26] Such electrical measurements were successfully experimented these last years in the field for root length density estimation [27] and root trait selection in wheat [28]. 3D capacitance tomography has been used as a root distribution probe in laboratory [29]
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