Plants may be stationary creatures — absorbing sunlight from the sky above and nutrients from the surrounding soil — but they also share important information about community conditions.
Plant communication isn't a new discovery, but the amount of detailed information and the how it's communicated is new ground, according a study published in the journal PLOS ONE. Using maize seeds, scientists tested whether or not aboveground communication between plants was passed along to other plants by belowground means, and, if there was communication, what was the response from the other plant?
It turns out there's a strong response: plants will adjust their growth based on stress cues passed on from other plants.
To determine how the plants communicated and to what extent, scientists grew a number of Zea mays L. cultivar Delprim seedlings. They gently brushed the maise leaves with a makeup brush to mimic the effect of another plant's touch. The plants were not damaged over the course of the experiment. Some plants were left untouched. The touched plants continued to grow in a hydroponic solution that allowed scientists to capture any chemical signals they released.
That growth solution was then used to help scientists conduct a few separate experiments.
The first involved planting new seeds in the solution containing the touched plants. The new seeds responded to the chemicals the touched plants released by growing more leaves and fewer roots. When new seeds were placed in the solutions of untouched plants, they grew leaves and roots at a more equal rate.
In the second experiment, plants were placed in a Y-shaped container. An untouched plant was placed at the intersection of the branches. One branch had the solution from the touched plant in it while the other had a fresh growth solution in it. In this "root choice" test, the untouched plant's roots would head for the branch containing the new growth solution, even if its roots were already growing in the direction of the branch containing the touched plant's solution.
The final test involved simply studying how untouched plants behaved when they grew next to plants that had previously been touched. These plants would simply grow bigger together.
"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," the researchers wrote. "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."
Based on the experiments, it seems clear that plants communicate about even something as innocuous as the touch from another plant. In the plant world, that's a big deal because it helps them avoid competing for space and resources – and that's important no matter what neighborhood you live in.