Volatile organic compounds (VOCs) act as a language that plants use for their communication and interaction with the surrounding environment. Released from leaves, flowers and fruits into the atmosphere and from roots into the soil, VOCs have been shown to be instrumental in plant-plant, plant-animal, and plant-microbe interactions. Plant-plant communication via VOCs includes first VOC release into the atmosphere to create a diffuse signal that is then perceived by neighboring plants. To be released from cells, VOCs have to move through multi-tier barriers and until recently it was accepted that emission occurs by passive diffusion. However, using biochemical and reverse genetic approaches, we demonstrate that active biological mechanisms are involved in transporting volatiles from plant cells to the atmosphere. We also show that the cuticle is not simply a passive diffusion barrier for VOCs to cross, but plays a more complex role in the emission process as an integral member of the overall VOC biosynthetic network. Using petunia as a model system, we discover a new physiological phenomenon: inter-organ aerial transport of VOCs via natural fumigation (that is, gas treatment of an enclosed space). Before petunia flowers open, a tube-specific terpene synthase produces sesquiterpenes, which are released inside the buds and then accumulate in the stigma, potentially defending the developing stigma from pathogens. These VOCs also affect reproductive organ development and seed yield, which is a previously unknown function for terpenoid compounds.
