Electrical Capacitance versus Minirhizotron Technique: A Study of Root Dynamics in Wheat-Pea Intercrops.

Imre Cseresnyés,Mária Megyeri,Tünde Takács,István Parádi,Anna Füzy,Bettina Kelemen,Ramóna Kovács,Péter Mikó

doi:10.3390/plants10101991

Abstract

This study evaluated the concurrent application and the results of the root electrical capacitance (CR) and minirhizotron (MR) methods in the same plant populations. The container experiment involved three winter wheat cultivars, grown as sole crops or intercropped with winter pea under well-watered or drought-stressed conditions. The wheat root activity (characterized by CR) and the MR-based root length (RL) and root surface area (RSA) were monitored during the vegetation period, the flag leaf chlorophyll content was measured at flowering, and the wheat shoot dry mass (SDM) and grain yield (GY) were determined at maturity. CR, RL and RSA exhibited similar seasonal patterns with peaks around the flowering. The presence of pea reduced the maximum CR, RL and RSA. Drought significantly decreased CR, but increased the MR-based root size. Both intercropping and drought reduced wheat chlorophyll content, SDM and GY. The relative decrease caused by pea or drought in the maximum CR was proportional to the rate of change in SDM or GY. Significant linear correlations (R2: 0.77–0.97) were found between CR and RSA, with significantly smaller specific root capacitance (per unit RSA) for the drought-stress treatments. CR measurements tend to predict root function and the accompanying effect on above-ground production and grain yield. The parallel application of the two in situ methods improves the evaluation of root dynamics and plant responses.

Highlights

Owing to methodological difficulties in assessing the growth and activity of intact root systems in the soil [1,2], the application and development of indirect, non-destructive techniques, including electrical methods, have received increasing attention in recent years [3,4].The electrical capacitance of the root–soil system (CR), measured using a low-frequency alternating current (1 kHz AC) between one electrode fixed to the plant stem base and another inserted into the surrounding soil, was reported to correlate with the root system size (RSS) [5]
CR and MR measurements were performed in the same intercrop system, aiming (i) to analyze and compare the results provided by the methods during monitoring the response of root dynamics of various wheat genotypes to intercropping and drought, and (ii) to evaluate the potential benefits of the simultaneous application of the two approaches
The presence of pea caused a decrease in wheat root capacitance; in general, this effect was significant from DAP 31 to DAP 88 (Table S1)

Summary

Introduction

Owing to methodological difficulties in assessing the growth and activity of intact root systems in the soil [1,2], the application and development of indirect, non-destructive techniques, including electrical methods, have received increasing attention in recent years [3,4].The electrical capacitance of the root–soil system (CR), measured using a low-frequency alternating current (1 kHz AC) between one electrode fixed to the plant stem base and another inserted into the surrounding soil, was reported to correlate with the root system size (RSS) [5]. Dietrich et al [8,9] suggested a revised model, and explored that CR was dominated by the stem base between the plant electrode and the substrate surface (with a negligible contribution of the roots), and was correlated with a stem cross-sectional area. According to their explanation, the CR–RSS correlations are merely due to the allometric relationship between root and shoot traits. Due to the allometry between the proximal root regions that mostly contribute to current flow and the distal fine roots responsible for solute absorption [8,9,10], CR is related to the water uptake activity of the root system (referred to as “root activity”) as a whole [6,14,15]

Methods

Results

Discussion

Conclusion