Development of Optical and Electrical Sensors for Non-Invasive Monitoring of Plant Water Status

Abstract

Monitoring plant water status is vital for optimizing irrigation in precision agriculture. This study explores the use of two simple, affordable, and non-invasive sensor systems, electrical impedance spectroscopy (EIS) and infrared (IR) spectroscopy, to assess plant water status directly from leaf tissues. This approach is well-suited for the realization of large networks of distributed sensors wirelessly connected to a central hub. An outdoor experiment was conducted over two phases of 20 day-experiment involving six Hydrangea macrophylla plants subjected to two irrigation treatments: a control group (well-irrigated) and a test group (poorly irrigated) designed to induce water stress. The standard relative water content (RWC) method validated the treatment effects on the plants, and both EIS and IR sensors effectively distinguished between the two groups. Impedance-derived parameters, particularly the normalized intracellular resistance (R0) and the cell membrane capacitance (C0), exhibited statistically significant differences between the treatments. In addition, the IR measurements showed moderate correlations with RWC, with determination coefficients of R2 = 0.56 and R2 = 0.51 for first and second phases of the experiment, respectively. Despite some limitations concerning the electrode–leaf conformity and external sunlight interference, the results point to the advantages of these methods for real-time plant monitoring and decision-making in smart irrigation systems.

Plant phenotyping relevance

植物の水分状態という生理形質を対象に、EISおよび赤外分光センサーによる非侵襲的測定法を開発・検証しており、センサー手法が研究の中心である。

Code and data availability

The paper's plant-phenotyping measurements (RWC, IR absorption, and impedance spectra from six Hydrangea macrophylla plants) are not publicly deposited; the Data Availability Statement requires contacting the corresponding author. The MDPI supplementary material only contains a representative waveform figure and a mete

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