Plants calling for help? Researchers have discovered that under certain conditions, plants may communicate with insects or other plants. Plant leaves emit into the air organic compounds called green leaf volatiles, or GLVs. Researchers Douglas Whitman and Fred Eller have made two interesting discoveries. First, damaged plants emit more GLVs than undamaged plants. In their study, damage was caused either artificially or by caterpillars eating leaves. Secondly, they demonstrated that certain wasps that feed on caterpillars will fly toward the source of GLVs. Together, these pieces of information suggest that plants under attack from caterpillars emit chemical signals that guide enemies of the caterpillars to sites where they have caused damage.
In another research project, Edward Farmer and Clarence Ryan demonstrated that plants might be communicating with one another. They showed that internal plant defense mechanisms are activated when plants are exposed to a chemical called methyl jasmonate. Methyl jasmonate is released into the air when leaves of a plant are damaged by herbivores. This may warn neighboring plants that herbivores are in the area, enabling them to chemically defend themselves from attack in advance.