plants growing

If your feet were planted in one place for your entire life, you’d probably come up with some pretty creative solutions for how to get along with your friends, family, coworkers, and neighbors. Fortunately, we can put in our headphones or move to another room if someone is all up in our space. Plants can’t, though, so they’ve learned how to be a little inventive when it comes to getting along, reported scientists in the journal PLOS One on Wednesday.

Scientists have long known that plants use chemical signals to communicate with one another, but in the new paper, researchers show that plants can respond to stress in a way that affects other plants too. In a series of experiments on corn (Zea mays L.) seedlings, a team of researchers demonstrated that a plant that modifies its growth based on physical contact with its neighbors will affect the growth of the other plants near it. In other words, its family and neighbors are sensitive to the stress it’s undergone and give it space.

plant stress response
When the middle plant touches another plant, it releases chemicals that can affect the growth of another plant that wasn't involved.

To conduct the experiment, scientists lightly touched the leaves of a few plants with brushes, being careful not to damage them. This simulated the plants being touched by neighboring plants’ leaves. Some of the other plants were left completely untouched. Then, the team tested how the soil beneath both touched and untouched affected the growth of other seedlings. In a “root choice” test, they found that the roots of new seedlings grew significantly more toward soil from untouched plants and away from the soil from touched plants when given the option. In another experiment, the researchers transferred new seedlings into the soil of touched plants and untouched plants. In this case, they found that the seedlings planted in the “touched” soil grew significantly more leaves and fewer roots than the plants in soil from untouched plants.

These experiments suggest that the stress-related chemicals released into the soil by plants when they’re touched have a significant effect on neighboring plants, helping the corn plants prevent overcrowding by communicating about when they’re getting a little too close for comfort. “Our results show that the above ground plant-plant communication by brief touch can provoke responses in nearby non-touched plants through below-ground communication,” write the study’s authors. “This indicates that responses to neighboring plants can be significantly affected by the physical conditions (in this case, mechano-stimulation) to which these neighbors are exposed to. It thus suggests that plant-plant below-ground communication is modified by above-ground mechanical stimulation.”

These results have implications for both the natural world and the laboratory. In the lab, this suggests that any slight contact a scientist might have with a plant could totally change the outcome of any plant experiments. Outside the lab, the results might not be quite as profound, but they suggest that plants are far from static, passive organisms.

In much the same way as you might get up and give your seat on the bus to someone who looks like they need to sit down, it turns out that plants are sensitive to the needs of their neighbors and adjust their habits accordingly. Maybe we could learn a lot from them.