Volatile communication among sagebrush branches affects herbivory: timing of active cues

Airborne communication can affect systemic induced resistance to herbivory on neighboring branches and individual plants. Sagebrush is the best known example of this phenomenon although the mechanisms of this communication system remain unidentified. We do not know the timing of emission or the chemical nature of the active cue. We investigated the timing of this phenomenon by using plastic bags to prevent propagation of volatile compounds and experimentally manipulated the timing of removal of these bags. We found that blocking the volatiles prevented systemic induced resistance. Experimentally allowing clipped branches to release cues for up to 3 days after clipping caused a reduction in damage in neighboring branches on the clipped plants. This indicates that active cues are released from the time we clipped for the next 3 days or that cues released immediately remained active over this time period. As we continue to evaluate potential chemicals as active cues in plant communication, this prolonged effectiveness may provide an important screen against which to evaluate any putative signals. Handling editor: Robert Glinwood