We all know someone who talks to their plants. And studies have shown that if you talk nicely to a plant every day, it will grow more lushly. Conversely, if you insult it, it will wilt. But are plants also able to talk to us?
A group of researchers from the school of plant sciences and Food Safety at Tel Aviv University, Israel, published a study in which they analyzed the sounds made by plants. It is known that plants manifest their moods through changes in color, smell or shape. However, this study group tackled a more surprising aspect: plants manifest their stress through sounds.
Several tomato and tobacco plants were chosen for analysis. The recordings were made in both a greenhouse and an acoustic chamber, in order to have as clean an auditory sample as possible. Sounds were then recorded 10 centimeters around each plant in its normal state, using ultrasonic microphones, capable of recording at frequencies of 20-250 kilohertz (humans can detect 16 kilohertz at most).
The sound is like “popcorn“.
The plant was then subjected to different stress situations: drought and cutting of some leaves (wounds), and recorded. “The sounds captured are similar to clicks, like popcorn bursting”, explain the scientists. Moreover, these sounds “are emitted at a volume similar to that of human speech, but at high frequencies, beyond the range of hearing of the human ear”. which explains why we cannot hear them. Specifically, the plants emitted sounds at frequencies between 40 and 80 kilohertz.
The plants spoke little if they were stable and much if they were stressed.
The study went further by isolating the sound waves and classifying them according to the condition of the plant. This revealed patterns that coincided depending on whether the plant was suffering from drought or injury. In other words, the plant was communicating exactly what was happening to it, with its own “words” to say “I'm thirsty” or “I'm in pain”. “We found that plants generally emit sounds when they are under stress, and that each plant and each type of stress is associated with a specific identifiable sound,” they explain.
Moreover, the greater the stress, the more sounds are picked up, up to dozens of sounds per hour. Under less stress, the plant seems to “speak” slowly and sparsely, emitting only a few sounds per hour. These sounds can be detected by certain animals, such as mice, insects, and bats, which are accustomed to high-frequency sounds in nature.
So we can say that even a quiet field of flowers can be a very noisy place, but we can't hear the sounds. The scientists were very excited about their findings, because “these sounds contain information, for example, about the lack of water or injuries. In addition, this research paves the way for understanding plant species and their interactions with the environment, as well as their potential use in agriculture.