Scientists from Tel Aviv University recorded and analyzed the sounds plants make when under stress. Article published in the journal cell.
Previous studies have shown that vibrometers attached to plants record different vibrations. However, it was not known whether these were converted into sounds that could be recorded remotely.
In the new study, the scientists placed the plants in an acoustic box without background noise. At a distance of about 10 centimeters from each plant, ultrasonic microphones were placed, recording sounds at frequencies of 20-250 kHz (the maximum frequency perceived by an adult is about 16 kHz).
The plants were subjected to various stresses before recording the sounds: they were not watered for five days or their stems were cut. Scientists have found that plants make sounds at frequencies of 40-80 kHz. The stress-free plants made, on average, less than one sound per hour. At the same time, dehydrated and damaged plants made dozens of sounds every hour.
The scientists noted that popcorn-like popping sounds are produced at a high level of human speech, but at high frequencies beyond the audibility of the human ear. They believe that some animals can pick up these sounds: mice, bats, and insects. Also, scientists don’t yet know how the sounds are formed, but they suggest they are related to oxygen bubbles bursting in plant tissues.
The resulting recordings were analyzed using machine learning (AI) algorithms. The algorithms learned to distinguish between different plants and different types of sounds and were eventually able to identify the plant and determine the type and level of stress from the recordings. The study focused mainly on tomatoes and tobacco, but wheat, corn, cactus and whitefly noises were also recorded.
In the future, scientists’ discovery may lead to the development of special sensors to monitor the state of plants.