If you’ve ever watched a time lapse video of a plant, you’ll be well aware that most plants are surprisingly active organisms. Whether it’s through changing their orientation to follow light, or through wriggling their roots to find the optimal path to grow, plants interact and change with their environment very often. Additionally, plants have a clear ability to pass information on to other organisms. For example, a plant will typically attract pollinators to sources of pollen with bright colors and sweet aroma. However, a topic that scientists have only been able to explore more recently is how plants actively communicate with each other.
When it comes to growing plants, conventional wisdom would suggest that plants would grow in a way that allows them to reach as many important resources as possible, but a 2018 study suggests additional factors, most notably the state of neighboring plants, also factor into the way plants grow. The study showed that very young maize plants direct their root growth away from neighboring plants when those neighbors are subjected to physical stresses (such as being touched). This was found to be caused, at least in part, by changes in the underground environment surrounding the observed plants. Despite the fact that the researchers were unable to detect significant changes in the compounds released by the roots of stressed and non-stressed plants, the seedlings’ roots showed clear preference for solutions taken from non-stressed plants, even when the solutions were isolated from the plants themselves.
This suggests that plants are able to influence each other’s behavior through creating very slight changes in below-ground conditions. This is consistent with another study, which examined whether stressed plants are able to induce stress responses in unstressed neighbors. This study found that not only do pea plants detect drought responses from plants with whom they share soil, but that those plants prepare for stressful conditions in such a way that is detectable to other plants even further away from the initially stressed plant. Even if they are in soil completely separated from the first plant, the information is passed on, inducing measurable changes in behavior along even a five-plant chain, almost like a game of telephone.
Other, broader studies suggest that plant behavior is largely selfish, meaning that the fact that plants can influence each other is more a byproduct of plant behavior than it is a specific goal. Plants respond to changes in their environment, especially sources of danger or stress, with behavior that can be detected by other plants, but being detected by other plants is not often, if ever, the goal of this response. There is little actual benefit to a stressed plant associated with broadcasting its state of stress to neighbors, and as a result scientists theorize that plants are more accurately described as having the ability to “eavesdrop” on each other, rather than directly communicating.
Even still, the ability to understand which environmental changes are the result of other individuals’ responses to stimuli is an example of just how finely tuned and complex plant behavior can be. While communication with other plants rarely benefits the plant spreading information, such phenomena benefits the species as a whole, which is why communication in this way is still an evolutionarily viable trait. So even though plants probably don’t have their own language or alphabet, there’s still a lot more information traveling between them than you may have ever realized!
