Influence of substrate type and properties on root electrical capacitance

Abstract

Three pot experiments were performed on cucumber, maize, soybean and wheat plants to investigate the effects of various substrate types, namely pumice, arenosol and chernozem soil (Exp. 1), of substrate salinity (Exp. 2) and of soil water content (SWC; Exp. 3) on the electrical capacitance measured in root-soil systems. The data were evaluated according to the basic principle of the two-dielectric capacitor model. Statistical analysis indicated that the capacitance measured in root-soil systems was determined by the capacitance of the root system for each combination of plant species and substrate. Furthermore, the results showed that substrate impedance had a negligible influence on the capacitance measured in root-soil systems. Substrate salinity had no direct effect on capacitance measured in root-soil systems, but salt-induced physicochemical changes in plant tissues could have influenced its dielectric properties. Capacitance measured in rootsoil systems increased exponentially with soil water content (it ranged from 10 to 48 v/v %), indicating that the measured capacitance was more sensitive to variability in moisture content at high rather than at low water saturation levels. This is not consistent with the general consensus that the capacitance method is unreliable in dry soil and should be used at soil water content close to field capacity. The present results will contribute to the more effective application of the root capacitance technique.

Root electrical capacitance as an indicator of wheat growth and yield in a free-air carbon dioxide enrichment (FACE) experiment

“…Variation in soil water content (SWC) has a marked effect on C R due to changes in soil-ground electrode contact (Ellis et al 2013) and in the root to soil conductance ratio (Gu et al 2021). A close positive relationship between C R and the SWC of the root zone was previously shown for several species (Cseresnyés et al 2018(Cseresnyés et al , 2020a. Using a species-specific exponential function, a saturation capacitance, C R * (which can be detected in watersaturated soil) was calculated from the measured C R and the corresponding SWC.…”

Root electrical capacitance as an indicator of wheat growth and yield in a free-air carbon dioxide enrichment (FACE) experiment

“…Variation in soil water content (SWC) has a marked effect on C R due to changes in soil-ground electrode contact (Ellis et al 2013) and in the root to soil conductance ratio (Gu et al 2021). A close positive relationship between C R and the SWC of the root zone was previously shown for several species (Cseresnyés et al 2018(Cseresnyés et al , 2020a. Using a species-speci c exponential function, a saturation capacitance, C R * (which can be detected in watersaturated soil) was calculated from the measured C R and the corresponding SWC.…”

Electrical impedance spectroscopy (EIS) in plant roots research: a review

“…This approach is now being applied to evaluate root responses to different alkalinity levels. In 2020, I Cseresnyes measured the root-soil system capacitors of cucumber, corn, soybean and wheat plants under different soil substrate components, different substrate salinity, and different water content at a single frequency [ 32 ]. The results show that the basement impedance and substrate salinity have negligible effects on the capacitance measured in the root-soil system.…”