As it turns out, Roald Dahl was onto something. If you damage a plant, it will scream..
Well, in a way. Not the same way you or I scream. Rather, they emit popping or clicking sounds at ultrasonic frequencies outside the range of human hearing that increase when the plant is stressed.
A study published in 2023 suggests that this may be one way plants communicate pain to the world around them.
“Even in a quiet field, there are actually sounds that we can’t hear, and those sounds contain information. Some animals can hear these sounds, and many acoustic interactions It could be happening.” Evolutionary biologist Lilac Hadani said: from Tel Aviv University, Israel.
“Plants are constantly interacting with insects and other animals, and many of these organisms use sound to communicate, so it’s very suboptimal for plants not to use sound at all.”
Stressed plants are not as passive as you might think. They undergo some pretty dramatic changes, one of the most notable of which (at least to us humans) is the release of a pretty powerful scent. You can also change the color and shape.
These changes can signal danger to other nearby plants, which increase their own defenses accordingly. or Attract animals to deal with pests It can harm plants.
However, whether plants emit other types of signals, such as sound, has not been well investigated. A few years ago, Hadani and his colleagues discovered that plants can detect sound. The next logical question to ask was whether they could produce it too.
To find out, they recorded tomato and tobacco plants under different conditions. First, we recorded unstressed plants to obtain a baseline. We then recorded dried plants and plants with severed stems. These recordings were first made in a soundproof acoustic room and then in a regular greenhouse environment.
They then trained a machine learning algorithm to distinguish between the sounds made by unstressed, cut, and dried plants.
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Plants make sounds like crackles and clicks at frequencies too high for humans to hear, and can be detected within a radius of more than 1 meter (3.3 feet). Plants that are not stressed do not make any noise at all. They just hang out and quietly work on the plants.
In contrast, stressed plants are much noisier, emitting up to about 40 clicks per hour on average, depending on the species. And plants deprived of water have a pronounced acoustic profile. Before any visible signs of dehydration appear, the ticking noise begins to get louder, escalates as the plant dries further, and subsides as the plant dies.
The algorithm was able to distinguish between these sounds and the types of plants that produced them. It’s not just tomatoes and tobacco. The research team tested a variety of plants and found that sound production is a very common activity in plants. Wheat, corn, grapes, cactus and henbit were recorded making noise.
However, there are still some unknown points. For example, we don’t know how sound is produced. Previous research has shown that plants that dry out experience cavitation, a process in which air bubbles form inside the stems, causing them to expand and collapse. This produces an audible popping sound when humans crack their knuckles. Something similar may be happening in plants.
It remains to be seen whether other distress conditions will also trigger the sound. Pathogens, attack, exposure to UV rays, extreme temperatures, and other adverse conditions can also cause your plants to burst like bubble wrap.
It’s also not clear whether sound production is an adaptive development in plants or just something that happens. However, the research team showed that the algorithm could learn to identify and differentiate plant sounds. It’s certainly possible that other creatures did the same thing.
Additionally, these organisms may have learned to respond to the noise of distressed plants in different ways.
“For example, moths that are trying to lay eggs on plants, or animals that are trying to eat plants, may be able to use the sounds to make decisions.” Hadani said.
For us humans, the effects are very obvious. We were able to tune into the distress signals of thirsty plants and water them before they became a problem.
However, it is unclear whether other plants sense and respond. Research results to date have shown that That plants can increase their power Drought tolerant that responds to soundSo it’s certainly plausible. And this is where the research team is pointing to the next stage of their research.
“Now that we know that plants actually make sounds, the next question is: Who is hearing the sounds?” Hadani said.
“We are currently investigating the responses of other organisms, both animals and plants, to these sounds, as well as their ability to identify and interpret sounds in completely natural environments.”
This research cell.
A previous version of this article was published in March 2023.
