Plants May Be Able To Communicate Each Other When They're Getting Crowded, Study Finds

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For years, scientists have theorized that plants may be able to communicate with one another. And according to a new study, while plants aren't exactly capable of chatting about the neighborhood gossip, neighboring plants may in fact be able to tell each other to stay off their lawns — or, well, to stay out of their growing area. The study, published May 2 in the scientific journal PLOS One found evidence that "plants can detect the presence of their neighbors and modify their growth behaviour accordingly," according to the study report.

Researchers on the study found "a new level of complexity" in belowground communication between plants that is triggered by aboveground interactions. That is, when the leaves of plants that are sensitive to crowding detect neighbors growing too closely, "plants can communicate a [biochemical, underground] warning message to their related neighbors, advising them to adjust their growth patterns accordingly," Gizmodo laid out.

In the study report, researchers explained, "Our results show that the above ground plant-plant communication by brief touch can provoke responses in nearby non-touched plants through belowground communication." They concluded their results indicate that a plant's "responses to neighbouring plants can be significantly affected by physical conditions [...] these neighbors are exposed to."

Lead study author Velemir Ninkovic, an ecologist at the Swedish University of Agricultural Sciences, told The Guardian that plants need some way to communicate when their neighbors are putting them in danger of being starved out of resources, because plants are largely sedentary. "If we have a problem with our neighbours, we can move flat," he said. "Plants can't do that. They've accepted that and they use signals to avoid competing situations and to prepare for future competition."

The Guardian explained that previously, scientists thought plants would alter their growth strategies based on physical touch, citing trees an an example, since they've "been seen to experience 'canopy shyness' and rein in their growth under crowded conditions." But this new study "reveals that this behaviour is driven, not just by mechanical cues picked up by leaves, but by chemical secretions in the soil," The Guardian reported.

To examine how plants may communicate, scientists working on the study used seedlings and "stimulated certain plants, gently touching the leaves 'from the base to the top...with a soft squirrel hair face brush,'" Atlas Obscura reported. Then the plants were left to "grow in a hydroponic solution, which would also capture any chemical signals from the plants' roots."

Ninkovic and his team completed three different experiments, and found that in all three, "the plants changed their growth strategy in response to the root signals from touched plants," according to Atlas Obscura. Specifically, when untouched plants were grown in a solution containing the chemical stress signal from touched plants, they "put more resources into growing their leaves and stems, instead of their roots," to avoid crowding.

Ninkovic told Atlas Obscura that he used to skeptical of plant-to-plant communication, "but over the past several years, a growing body of evidence has shown that plants are paying much more attention, in their particular plant way, to the world around them than we realized." Now he's interested in figuring out what signals plants send and how they're used. Further study could answer questions like, "Which signals are the most important and when?" and "How do plants take all the information available to them and change their behavior accordingly?" according to Atlas Obscura.

If you're having flashbacks to The Happening, in which trees band together to kill off humans in an effort to ensure their survival, don't worry too much. The results Ninkovic and his team obtained seem to show definite communication between plants, but it doesn't appear to be that sophisticated.

The full extent of what we could learn from this study is still uncertain, though; researchers concluded that the ecological significance of their findings will need to be further explored in future studies.