Plants produce sounds bij ticking, clicking and or popping ultrasonic frequencies that increase when plants get stressed. Humans cannot hear or detect this ultrasonic sounds.
We think plants produce sounds to comunicate when there is danger in some kind of way they want to warn other about. These sounds exist in silence, we do not hear them. But some animals do! This means there is some kind of interaction taking place between different organisms, as with insekts.
Some plants can do create other signals as well, noticable, as smells, colour change and shapes. These signals can cause changes by the other plants to defend or protect themselves, as atract animals to kill pests.
However, whether plants also emit other types of signals, such as sounds, had not yet been fully explored.A few years ago, researchers discovered that plants can detect sound .The logical next question was whether they could also produce it.
To find out, they recorded tomato and tobacco plants under different conditions.First, they recorded unloaded plants to get a baseline.Then they recorded plants whose stems had dried out and whose stems had been cut.These recordings took place first in a soundproof acoustic chamber and then in a normal greenhouse environment.
Then they trained a machine learning algorithm to distinguish between the sound produced by unstressed plants, cut plants and dried-out plants.The sounds emitted by plants resemble popping or clicking noises at a frequency far too high to be perceived by humans, and detectable within a radius of more than a meter.Unstressed plants don't make much noise at all; they just hang around and quietly do their plant thing.
Stressed plants, on the other hand, are much noisier, emitting an average of about 40 clicks per hour, depending on the species.And plants without water have a noticeable noise profile.They start clicking more before they show visible signs of drying out, and escalate as the plant dries out more, before subsiding as the plant wilts.
The algorithm was able to distinguish between these sounds, as well as the plant species emitting them.And it's not just tomato and tobacco plants.The team tested a variety of plants and found that good production seems to be a fairly common plant activity.Wheat, corn, grape, cactus and henbit were all included and made noise.
But there are still a few unknowns.For example, it is not clear if noise production is an adaptive development in plants, or if it is just something that happens.However, the team showed that an algorithm can learn to identify and distinguish plant sounds.It is certainly possible that other organisms could have done the same.
Moreover, these organisms could have learned to respond in different ways to the sound of distressed plants.For example, a moth planning to lay eggs on a plant or an animal wanting to eat a plant could use the sounds to make its decision. For us humans, the implications are pretty clear; we could tune in to the distress cries of thirsty plants and water them before it becomes a problem.
But whether other plants perceive and respond to this is unknown.Previous research has shown that plants can increase their drought tolerance in response to sound , so it's certainly plausible.And this is where the team pinpoints the next phase of their research.
Now that we know that plants emit sounds, the next question is, "Who might be listening? We are currently investigating the responses of other organisms, both animals and plants, to these sounds, and we are also exploring our ability to identify and interpret the sounds in completely natural environments.
Fascinating to realize and know plants do communicate in so many ways!
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