Direct and in situ observations of plants under various light illumination conditions using electrochemical impedance spectroscopy

Abstract

The possibility of using electrochemical impedance spectroscopy (EIS) for direct and real-time monitoring of plants was investigated. Since EIS is an in situ monitoring technique and the obtained signals tend to reflect the ions in plant cells and tissues, it can be used to observe the ion fluctuations that result from the changes in the lighting conditions. Changes in EIS signals and the fitted parameters were observed upon application of an external stimulation to a Marchantia polymorpha individual, which has been known to cause the movement of calcium ions in cellular tissues. In addition, the EIS signals and fitted parameters also changed by altering the lighting conditions. Although further investigation is required, these fundamental experiments indicate that EIS could be applied to monitorin situ ionic phenomena that occur in plants.

Possibility of directly sensing plant stress under environment temperature changes using electrochemical impedance spectroscopy

“…22) Furthermore, we have been investigating changes in each piece of information obtained by applying physical stimulation, light stimulation by white light intensity, and light stimulation at specific wavelengths via calculations using an equivalent circuit reflecting the structure of each cellular tissue and fitting the EIS signal. 23) For practical use, clarifying the relationship between several external factors of plants and EIS signals is indispensable. In this study, the change in the EIS signal under temperature environment changes was investigated by directly monitoring plant leaves.…”

“…We reported that the investigation of the response to environmental changes can be observed using EIS measurements of Marchantia polymorpha, a basal plant with a relatively simple genetic structure, suggesting that EIS measurements can be applied to a wide variety of terrestrial plants. 23) In fact, we reported a study using a similar EIS measurement system to measure Petunia, which are ornamental plants. 22) Moreover, in a previous study, potato, 24) rhododendrons, 25) and golden pothos 26) were used to examine plant responses to temperature changes using electrical measurements.…”

“…A frequency-response analyzer (IM3533-01, HIOKI, Japan), with frequencies ranging from 10 Hz to 200 kHz, was used for the EIS measurements. For all EIS measurements, a 20 mV AC signal was applied to the Primula plant; this voltage does not seriously affect the cellular tissues 22,23) of the plant. The Primula was placed in a temperature-controlled greenhouse and measured under non-sunlight conditions to avoid the effects of changes in light intensity.…”

“…The fitting curve obtained using the proposed model was consistent with the experimental data. The Okajima model was used for the equivalent circuit of the fitting of cellular plant tissues, 22,23) as shown in Fig. 1(b).…”

“…The details of the equivalent model are available in our previous papers. 22,23) The equivalent circuit of the cellular tissue [right side of Fig. 1(b)] contains four elements: a series resistance (Ri), parallel resistance (Rm) and the constant phase element, CPE, as the "capacitance-like element" of a parallel circuit, and a resistance (Ro) of the parallel with the rest circuit.…”