Plants breathe, sweat and they might even talk!
According to research carried out in Israel, some plants are capable of emitting ultrasonic airborne sounds in quick bursts when they lack water or if they are subjected to some form of external aggression, for example if their stem is cut.
Plants emit ultrasonic airborne sounds. This is an observation that researchers actually made in 2019, based on the results of an experiment conducted in Israel.
Three years later, their findings have now been published in the journal Cell. According to the study, led by Lilach Hadany (a biologist and evolutionary theorist at Tel Aviv University), stressed plants can produce about 50 of these sounds in less than an hour, whereas they generally produce less than one sound per hour if they are healthy.
This difference is not perceptible to the human ear, but some animal species, such as moths or rodents, may be able to hear them from a distance of three to five meters, according to the researchers’ estimates.
To reach these conclusions, the researchers made sound recordings of tomato and tobacco plants grown in a greenhouse and placed inside an acoustic chamber. According to their observations, the frequency of these ultrasonic sounds seems to step up after two days without water, before increasing further until peaking on the fifth or sixth day.
Among other things, the study explains that when plants are exposed to drought stress or stem cutting, they undergo a process called “cavitation,” in which air bubbles form, expand and burst in the plant tissue (xylem), giving rise to vibrations that could explain the origin of these sounds.
“These findings can alter the way we think about the plant kingdom, which has been considered to be almost silent until now,” the study authors write.
Although they have not been able to determine whether these are actually calls for help from plants or simply a purely physiological response, the researchers point to the need for further research in the field of plant bioacoustics.
“A potential application of our results can be for monitoring plants in the field or greenhouse. Specifically, plant sound emissions could offer a way for monitoring crops water and possibly disease states — questions of crucial importance in agriculture. More precise irrigation can save up to 50% of the water expenditure and increase the yield, with dramatic economic implications,” the researchers write.
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