Each plant makes high-pitched sounds when subjected to stress. The sound emitted is quite loud and can be heard from several meters away in part by humans, other animals, insects and other plants. These sounds were recorded by a team directed by Itzhak Khait at Tel Aviv University in Israel, and subjected to an artificial intelligence program which was able to predict from just listening to the sound emitted even in the midst of ambient noise, the state of the plant as dried, cut or intact.
When the plant is intact and healthy it emits very few practically negligible and often not even detectable sounds, it practically remains silent, while when it is subjected to stress the ultrasound is clear, detectable and acute.
The emission of sounds is produced by cavitation, the production of small bubbles inside stressed plants. Some plants are more talkative than others, for example the whine of the tomato is three times more frequent than tobacco, and also the "motivations" are different, for example some plants make more noise if they have little water rather than being damaged.
Animals such as humans can hear, only if in perfect health, a part of the sounds emitted by plants, while other mammals such as bats, for example, are able to clearly hear the entire spectrum of sounds emitted, and therefore it is hypothesized that for they think a forest is too noisy to sleep in, or that insects such as moths, which in the same way hear perfectly the whole range of sound emissions from plants, prefer to lay their eggs on healthy and therefore more silent trees.
The studio Is There a Role for Sound in Plants? published on the Plants (Basel, Switzerland), said: "Plants have long been considered passive, static, and unchanging organisms, but this view is finally changing. More and more knowledge is showing that plants are aware of their surroundings, and they respond to a surprising variety of stimuli by modifying their growth and development Plants extensively communicate with the world around them, above and below ground.
Although communication through mycorrhizal networks and Volatile Organic Compounds has been known for a long time, acoustic perception and communication are somehow a final frontier of research. Perhaps surprisingly, plants not only respond to sound, they actually seem to emit sound as well.
Roots emit audible clicks during growth, and sounds are emitted from xylem vessels, although the nature of these acoustic emissions still needs to be clarified. Even more interesting, there is the possibility that these sounds carry information with ecological implications, such as alerting insects of the hydration state of a possible host plant, and technological implications as well.
Monitoring sound emissions could possibly allow careful monitoring of the hydration state of crops, which could mean significantly less water used during irrigation. This review summarizes the current knowledge on sound perception communication in plants and illustrates possible implications and technological applications."