Plants emit ultrasound when subjected to water stree or tissue damage to alert other plants of the danger
He is about to end up run over, his mother saves himWe are used to considering plants as immobile beings, helpless, unable to communicate or perceive the surrounding environment.
The reality, however, is very different and, if trees and plants were not able to communicate with each other and reacting to external conditions they could not defend themselves and could not survive on Earth for hundreds of millions of years.
We have long known that one of the defense and communication strategies of plants occurs thanks to the production of volatile molecules which act as a call for pollinating insects, as a repellent for predators or which can serve to warn other species about imminent dangers.
Another modality of plant communication consists in the emission of ultrasounds and it is precisely on this strategy that the researchers of the Tel Aviv University have concentrated.
The recent study investigated the ability of plants to generate sounds under stressful conditions, including water shortages or stem cutting.
The researchers tested the tobacco and tomato plants, placing microphones about 10 centimeters and subjecting the crops to drought conditions and damage to the leaves and stems.
Following stressful events, the plants shed ultrasound between 20 and 100 kilohertz, a frequency not perceptible to the human ear but detectable by other organisms up to several meters away.
The research found that the number of "ultrasonic screams" emitted by the plants varied according to the type of stress they were subjected to.
The tomato plants to which it was cut the stem they let out about 25 screams per hour, while those of tobacco that suffered the same damage generated 15 screams every hour.
When the plants were deprived of water the number of sounds detected has changed: in tomatoes they increased to 35 per hour, while in tobacco they dropped to 11.
Plants that have not undergone any type of stress, instead, emitted only one sound within 60 minutes.
Why do plants scream when subjected to stress and why does the number of screams vary based on the stress they experience? It is probably one strategy to warn other species not only of the imminent danger, but also to offer information on the type of danger, so that other specimens can put in place specific defense mechanisms to deal with the situation in the best way.
The results of the study, in addition to making us question the idea that the plant world is silent, offer an interesting tool that could be exploited in research and agriculture.
To understand better the sound emission and the interactions with the environment of plants, however, further investigations are necessary to analyze, for example, the impact of diseases, salt stress and changes in temperature on the production of sounds.
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