Recently, a study published in the bioRxiv preprint database and retrieved by Live Science, suggests that, just as people when stressed let out a cry of anguish or a shriek, plants that are in the same situation do the same.
Researchers at the University of Tel Aviv, Israel, placed microphones near stressed drinking and tobacco plants. Then, the instruments they used for the measurement captured ultrasonic squeaks about 10 centimeters away. The noises were observed to be within a range of 20 to 100 kilohertz. This is a distinct volume that can “be detected by organisms from up to several meters away.”
If people are not able to catch these screams it is because the frequency of the plants is too high and escapes our listening range, researchers say.
The study also reveals that animals and plants can hear and react to these “silent screams,” humans, with the necessary tools, can do so as well.
According to Anne Visscher, a member of the Department of Plant Biology and Comparative Fungal at Roya Botanic Gardens in the United Kingdom, in an interview for New Scientist:
“The suggestion that the sounds that drought-stressed plants make could be used in precision agriculture seems feasible if it is not too costly to set up the recording in a field situation.”
Like animals, plants respond to stress in different ways. Studies suggest that plants are able to release smelly chemical compounds or change their color and shape in response to drought or hungry herbivorous bites.
In the Live Science article, they point out that “Animals seem to recognize and respond to these botanical stress signals, and even other plants appear to pick up on the airborne scents wafting from their tense neighbors. Some previous research had suggested that plants react to sound, too, but questions remained about whether plants themselves emit detectable noises.”
The Tel Aviv team installed microphones near stressed tomato and work plants that they placed in a soundproof box in an open space in a greenhouse. The scientists subjected a set of crops to drought conditions and other physical damage, such as a cut stem. To verify their findings, the researchers used a third healthy and intact plants that served as a control group.
The data revealed that different plant species emitted different sounds at varying rates, depending on their stressful factor. Tomato plants stressed by drought emitted about 35 ultrasonic squeaks per hour, on average, while those with cut stalks produced around 25. Dried tobacco plants emitted about 11 shouts per hour, and the crops that were cut produced approximately 15 sounds at the same time. In comparison, the average number of sounds emitted by intact plants fell below one per hour.
Given the variation in noise between the groups, the researchers wondered if they could identify each plant based solely on its characteristic screams. Using machine learning, a type of artificial intelligence algorithm, the team selected different characteristics in each set of sounds and successfully classified their plants into three categories: dry, cut or intact. Someday, farmers could use similar technology to listen to crops stressed by drought in their fields, the authors suggested. Along with their experience and applying these findings to their work, farmers will definitely be outstanding in their fields.
