EAGER: Interrogating Plant Volatile Reports About the Environment

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Plants rapidly detect and respond to changing conditions. This makes them sensitive indicators of environmental events. Odors, or "volatile organic compounds" (VOCs) are actively emitted by plants in response to stresses, including drought, disease, and insect attack. The mix of VOCs provides a "fingerprint" of what the plant has experienced. VOCs can attract beneficial enemies of pests attacking a plant. For example, parasitic wasps are drawn to plants being eaten by the insect the wasps are seeking. VOCs are also thought to "cue" neighboring plants about imminent danger. Healthy plants exposed to odors from damaged or diseased plants initiate defense responses that may help them survive. VOC concentrations are very low, so all experiments on their ecological roles have so far been done indoors. No one has yet sampled VOCs functioning in open air, or in natural settings. This project will produce a new VOC-sampling and analysis instrument capable of characterizing plant response "fingerprints" in open air. This project will employ a novel chemical sensor based on laser photonics and microfluidics, called an opto-fluidic ring resonator (OFRR). The OFRR requires a sample volume of only 20 nano-liters and so can detect and identify VOCs at extremely low concentrations. In a series of experiments done with purchased odors and then with real plants, the OFRR will be refined to analyze plant VOCs at concentrations well below the current state of the art. The device will be used to demonstrate for the first time that VOCs emitted by one plant really do travel to and turn on responses in another plant in open air. Besides confirming a long-held and important scientific hypothesis, this project offers numerous valuable technical applications. These include the ability to sense pests damaging individual plants for economical spot-treatment, using plants as monitors of environmental quality, understanding complex plant-insect interactions, and post-harvest food quality and safety assessment. The project will train undergraduate and graduate students in a unique engineering/biology interaction, and will serve as an important component of the Bond Life Science Center's extensive science education and outreach program.