Study of Plant Bioelectric Potential Response Due to Photochemical Reaction and Carbon‐Fixation Reaction in Photosynthetic Process

Abstract

SUMMARY We focused on measurement of the bioelectric potential as a method of evaluating plant activities and supporting effective cultivation. In this study, we investigated the bioelectric potential response due to photochemical reactions and carbon‐fixation reactions in the process of photosynthesis. First, we measured the bioelectric potential when illumination was started and stopped, under N2 gas conditions in order to suppress the carbon‐fixation reaction and respiration. It was found that the amplitude of the potential response was related to the illumination intensity and the wavelength. We considered that the amplitude of the potential response under N2 conditions indicated the activity of the photochemical reaction. Based on this result, we investigated the potential response under room air conditions. If the carbon‐fixation reaction was deactivated by a long dark period, a significant potential decrease was observed when illumination started. In contrast, if the carbon‐fixation reaction remained active during a short dark period, the potential decrease was slight or none regardless of the photosynthetic rate. Therefore, we considered that this potential decrease is related to the activation of the carbon‐fixation reaction. Next, we investigated the relationship between plant activity and the potential response when illumination stopped. The results showed that the amplitude of the response is related to the illumination intensity and the respiration rate. We conclude that plant activities such as photosynthesis can be evaluated in more detail by measurement of the bioelectric potential, as an application of this study. © 2013 Wiley Periodicals, Inc. Electron Comm Jpn, 96(12): 85–92, 2013; Published online in Wiley Online Library (http://wileyonlinelibrary.com). DOI 10.1002/ecj.11518

Analysis of Plant Bioelectric Potential Response to Illumination by Curve Fitting

“…the carbon-fixation reaction, because the carbon-fixation reaction is deactivated slowly during a dark period. (8) On the other hand, we found that two common peaks of the potential rise and drop can be seen in Figs. 2-4.…”

“…It has been reported that the potential rise to illumination is related to the photochemical reaction and the following potential drop is related to the carbon-fixation reaction. (6,8,11) In addition, many studies also reported that the photosynthetic rate is related to the amplitudes of these potential rise and drop as well as the amplitude of the whole response V on . (6,7) On the other hand, when the illumination was stopped, the potential dropped sharply, and then recovered to the resting potential.…”

“…We have reported that the intensity of illuminating light correlated with the amplitude V off , and have considered that V off indicates the intensity of the photochemical reaction, which occurred until the illumination was stopped. (8) The amplitudes of these responses to illumination generally range from 10 to 20 mV under sufficient light intensity.…”

“…9 shows the potential response induced by illumination under the N 2 gas condition, which we reported previously. (8,11) In N 2 gas, the carbon-fixation reaction is inhibited owing to the CO 2 -free condition. In addition, both amplitudes, V on-N2 and V off-N2 , correlated with the intensity of illumination.…”

“…In the worst case of their overlap, significant information about the potential response was lost, and we were not able to evaluate the plant activities using the amplitude of the potential response, which was one of the conventional methods. (8) Otherwise, the integration value and frequency characteristic of the bioelectric potential are often used for the detailed analysis of the potential response. (9,10) These methods are effective for evaluating the resting potential and periodic response.…”