Stressed plants sonorally denote their state
2023/03/30 Galarraga Aiestaran, Ana - Elhuyar Zientzia Iturria: Elhuyar aldizkaria
One study has shown that the sound emitted by stressed iron and tobacco plants spreads through the air and can be detected up to a meter. It has been published in the journal Cell and states that dry plants or cut stems emit sounds with a volume similar to that of human conversation. People are not able to hear those sounds because their frequency is too high for people, but researchers say that it's very possible for other mammals and insects to hear them and probably other plants.
Sound emitted by stressed plants, with decreased frequency to be heard by humans. Kaith et al. CC BY-SA
It was already known that plants emit ultrasonic waves. They have now demonstrated for the first time that these waves are airborne. Given that the sounds emitted by animals also spread in this way, researchers believe there will be some communication between species.
In the experiment, healthy and stressed plants were recorded, in a soundproof chamber and in a (noisier) greenhouse. They caused two kinds of buds, some drying and others cutting stems. They then compared the recordings of each other using an machine learning algorithm. So they saw that healthy plants are very quiet. On the contrary, those suffering from a lack of water started issuing a few clicks and reached the maximum of the acoustic earthquakes on day 5. From that moment on, they gradually kept quiet until they were completely dried.
The algorithm is able to distinguish between the sound emitted by dried plants and that of cut stems, as well as whether the plant is tomato or tobacco. They also received sounds from other plants, but they still don't know exactly how they are produced. They think it can be because of the bubbles that are created in the plant's pipe system, but they accept that they have to continue to investigate to clarify. In addition, they consider it interesting to investigate interspecies communication and how to use this information in agriculture.