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MONTHLY NEWS January 1998 Listening to the Voices of Plants |
A researcher in Ibaraki Prefecture has developed a system that can "hear" what plants are saying. The messages sent by the plants are being used to determine when and how much to water them.
After years of research, Satomi Okushima, a scholar at the National Research Institute of Agricultural Engineering, developed a method of capturing the "voices" of plants--technically known as acoustic emissions (AEs). These emissions are air bubbles released by plants when they suck water through their roots. Because AEs are inaudible to human ears, ultrasonic sensors are applied to stems like stethoscopes. "The emissions sound like clicks," Okushima said. "Even though plants don't move around like animals, they seem much more alive when you can actually hear them." Okushima tested the new system on fruits and vegetables like melons and tomatoes. She found that AEs were most frequently perceived when the fruits were exposed to the morning sun. This is because their leaves dry out, and so they start absorbing water through the soil, producing more AEs. At such times, the plants produce about 300 "clicks" an hour, and the more AEs are produced, the more water plants need, according to Okushima. Okushima devoted nearly seven years to fine-tuning the system. The hardest part was determining how much water to give depending on the conditions under which plants are growing. The new technique is now being applied on an experimental basis to cultivate melons at the National Agricultural Experiment Station in Shizuoka Prefecture. Okushima says that the system could eventually help plants grow in the desert and other areas where water supply is limited.
Photo: Satomi Okushima applies an AE sensor to a plant stem. (Asahi Shogakusei Shimbun) 
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