In the world of plants, communication takes place by means of volatile chemicals released into the environment.
Scientists always thought this sort of communication wasn't very specific. If one plant produced a chemical message, any plant in the immediate vicinity could receive the message. They have since found that plant families produce different blends of volatile communication chemicals, with relatives producing the same blend.
Are plants like animals, they wondered. Would they pay more attention to messages sent by their closest relatives than by unrelated plants?
For many plant species, when insects chew the leaves of a plant, that plant releases chemicals that warn the surrounding plants of a possible attack. The receiving plants, in turn, produce toxic chemicals that repel the insects. Sagebrush is one of those plants.
To determine if responses to chemical signals differed between related and unrelated sagebrush plants, scientists used DNA fingerprinting to determine which individual plants were most closely related to each other.
Next, scientists took on the role of insect predators by experimentally clipping the leaves of certain sagebrush plants. Those plants would then produce volatile warning communication chemicals. Neighboring unclipped plants were both related and unrelated to the clipped plants. The question was, which unclipped plants would receive the message and make chemicals to repel insects?
Scientists measured insect damage to determine which plants received the warning message. They found that related plants had less insect damage by the end of the growing season than those more distantly related.
These results showed that plants can respond differently to volatile chemical messages from surrounding plants. They prefer to listen to messages from their own relatives rather than strangers.