Plants don’t have a nervous system, but they do seem to have a method for communicating with one another. In a way, it’s like their own kind of nervous system.
In animals, excited nerve cells secrete glutamate, an amino acid, which travels to the next nerve cell like a wave. Signals can thus go a long way. In plants, glutamate can have a similar effect.
Researchers studying how gravity affected plants created a sensor that detected calcium levels; it glows brighter as levels increase. In a test, they cut a plant leaf, then watched as the wound glowed and dimmed; then the glow appeared further away - it was a calcium wave. Glutamate was then confirmed as the stimulus for that wave. Learn more from the video by Science.