A plant-plant interaction mediated by volatile organic compounds (VOCs) was incidentally found when a potted poplar plant was placed nearby a mechanically damaged conspecific plant. In that case, the plant accumulated higher amounts of polyphenols probably because it perceived VOCs emitted from the wounded plant. Until now, a long list of reports on plant-plant communications mediated by VOCs has been brought about, and it is widely accepted that plants perceive VOCs formed by plants and microbes. However, it is uncertain what kind of perception mechanism is involved in the communication. One possible mechanism for carbonyl compounds is induction of detoxication mechanism plants usually employ against xenobiotics. Upon revealing underlying mechanism of VOCs perception by plants, it might be possible to innovate a novel strategy for sustainable agriculture.