Plant-plant signaling:: Ethylene synergizes volatile emission in Zea mays induced by exposure to (Z)-3-Hexen-1-ol

Leaf alcohol (Z)-3-hexen-1-ol (Z-3-ol) is emitted by green plants upon mechanical damage. Exposure of intact maize plants to Z-3-ol induces the emission of a volatile blend that is typically released after caterpillar feeding and attracts natural enemies of the herbivores [herbivore-induced volatile organic compounds (HI-VOC)]. Thus, it has been suggested that Z-3-ol might have a function in indirect plant defense mediating plant-plant signaling and intraplant information transfer. Here, we demonstrate that HI-VOC induction by Z-3-ol is synergized by the phytohormone ethylene. Exposure to Z-3-ol at doses of 100 and 250 nmol induced HI-VOC emission in intact maize plants. HI-VOC emissions increased by 2.5-fold when ethylene was added. The effect of ethylene was more pronounced (5.1- to 6.6-fold) when only total sesquiterpene release was considered. In contrast, ethylene alone had no inductive effect but rather decreased the emission of the constitutive maize volatile linalool. We suggest that ethylene plays a synergistic role in plant-plant signaling mediated by green leaf volatiles.