Okay, so plants don’t actually talk like we do, but they have developed some pretty interesting ways to communicate. One of the main ways they use is with volatile organic compounds (VOC). By varying the composition and concentration of the chemicals released with the situation plants are able to convey specific messages to other plants and animals.
Say a plant gets attacked by an herbivorous insect. The attacked plant may then release a certain mix of VOCs that notify the surrounding plants of the attack, causing them to strengthen their own defenses. The VOCs can carry information about the specific nature of the attacker, allowing the surrounding plants to enact more directed responses. The VOCs also allow the plant to “call in reinforcements” so to speak, by alerting predators and parasites of the herbivores to their location. Finally, the VOCs also serve, in some instances, to make the plant less appetizing.
As far as we know (there is still a lot of research to be done in this area) not all plant species do this. Some of the ones that do include sagebrush, lima beans, tomatoes, corn, poplar, and sugar maple trees. These signals are not species specific though; some plants can detect and respond to a warning even if the plant sending it is of a different species.
Plants don’t only “talk” about their problems. They also use VOCs and visual cues to communicate information about the quality and abundance of nectar and pollen to animals that visit the flowers. This allows plants to increase the likelihood of pollinations and ensure reproduction. Plants have also been known to release chemicals from their roots to ward off the roots of other plants when they start encroaching on valuable resources. These substances can also serve as an anti-microbial defense against microbes in the root zone.
Now, it bears saying that intent to communicate is impossible for plants. No plant thinks, “Oh, no! I’ve been attacked. Better tell my neighbors so they can protect themselves” because plants can’t think. Still, through evolutionary pressures they have developed ways to communicate about pests, reproduction, “personal” space, and a variety of other topics, which I think is pretty cool!
Witzany, Günther. “Plant Communication from Biosemiotic Perspective.” Plant Signaling & Behavior 1.4 (2006): 169-78. Web.
Ueda, Hirokazu, Yukio Kikuta, and Kazuhiko Matsuda. “Plant Communication: Mediated by Individual or Blended VOCs?” Plant Signaling & Behavior 7.2 (2012): 222-26. Web.
Karban, Richard. “Plant Behaviour and Communication.” Ecology Letters 11.7 (2008): 727-39. Web.