A groundbreaking study has revealed that plants emit sounds when they experience distress. Researchers at Tel Aviv University recorded faint ultrasonic clicks from stressed plants. These sounds, which occur at frequencies between 20 and 100 kilohertz, are inaudible to humans. However, organisms such as bats, mice, and moths could potentially detect them. Professor Lilach Hadany, the study's senior author, stated that even quiet fields contain sounds.
The research team recorded tomato and tobacco plants using ultrasonic microphones in controlled settings. Plants were stressed by withholding water for several days or by cutting their stems. Stressed plants emitted approximately 30 to 50 clicks per hour at irregular intervals. In contrast, unstressed plants produced fewer than one sound per hour on average. The sounds were about 60 to 65 decibels, comparable to normal human conversation.
A machine learning algorithm was subsequently trained to classify these acoustic signals. It could accurately differentiate between dehydrated plants, physically damaged plants, and healthy ones. Furthermore, water-stressed plants had begun emitting noises before visible signs of dehydration appeared. The researchers also found that corn, wheat, grape, and cactus plants produced similar sounds.
The precise mechanism behind these emissions remains uncertain, though scientists suggest cavitation as a cause. Cavitation occurs when air bubbles form and burst inside a plant's vascular system. These findings could have significant implications for agriculture and ecological research. Monitoring plant sounds might enable farmers to improve irrigation efficiency and conserve water resources.