Study on the AE Measurement and Activity Monitoring of Living Plants in Outdoor Environment using Electret Sensors
Kensuke Kageyama
Abstract
Transpiration of living plants causes the cavitation in the xylem and the acoustic emissions (AE) emitted during transpiration can be measured to monitor the activity of the plants. In this study, electret sensors (ECS) and IoT devices were prepared at low cost and the long-term plant AE measurements in outdoor environments of strawberry greenhouses and tea plantation were carried out. In greenhouse-grown strawberries, AE determination was performed considering as noise if AEs were detected more than once per second. Most AEs occurred during the daytime, and AEs caused by transpiration-induced cavitation could be measured. Furthermore, the correlation between the center of gravity (WH) of the AE occurrence hour of day and fruit quality was examined, and it was found that the later the WH, the higher the sugar content of the fruit. On the other hand, a large number of AE were detected due to rainfall when the AE determination was conducted on tea trees in the open field. Such an AE occurrence due to rainfall was eliminated by neglecting AE occurrence when soil moisture increased. Then, the 7-day moving average of the daily AE generation showed a strong correlation with soil temperature. These results indicate the possibility to monitor AE in outdoor environments such as greenhouse cultivation and open field cultivation using ECS and IoT devices.