The role of VOCs in within-plant signaling and systemically acquired resistance following herbivory in Datura wrightii

The production and emission of volatile organic compounds (VOCs) is ubiquitous across many plant species and has been implicated in a wide variety of defensive/resistance functions. One role that was recently uncovered is the ability of VOCs to function as an airborne signal to communicate damage within-plant. Following the perception of VOCs emitted by herbivore damaged tissue, yet-undamaged parts of the plant may then either induce or prime defensive responses in preparation for future herbivory. One benefit of an airborne versus a functionally similar vascular signal has been suggested as the ability to overcome vascular restrictions that may exist in plants with complicated orthostichy.

In a set of manipulative experiments, we differentially expose undamaged (receiver) leaves to VOCs emitted following local herbivory at another leaf (emitter) on the same plant. We then damaged receivers and measured the subsequent local VOC production at each leaf. Finally, we elucidated the orthostichy between emitter and receiver leaves. We analyzed the VOCs produced by receivers based on 1) exposure to airborne VOCs from the emitter and 2) vascular connectivity to the emitter in order to discern the relative contribution of each signal pathway in the formation of the overall systemic defensive response. We found that airborne exposure primed subsequent VOC production and restored the primed response to vascularly disconnected receivers. These findings illustrate the importance of VOCs as an airborne signal to communicate damage to yet-undamaged plant tissue with poor vascular connectivity and reinforce its multiple functions in plant defense/resistance.