One potential approach to understanding volatile communica- tion involves using transgenic or mutant plants that are genetically modified in their potential to emit or receive VOC signals. In the current study, we used transgenic tobacco plants emitting (E)-b- ocimene [(3E)-3,7-dimethyl-l,3,6-octatriene] as emitters for plant- plant communication assays. The acyclic monoterpene hydrocar- bon b-ocimene was recently found to induce increased tissue levels of methyl jasmonate and transcript levels of defense/stress- inducible genes in Arabidopsis [16]. Furthermore, transgenic Arabidopsis plants expressing a GUS-reporter gene under the control of the potato proteinase inhibitor II promoter (pinII) responded to several structurally different cyclic and acyclic monoterpenes (including b-ocimene). This is in line with the finding that six volatile terpenes increase the cytoplasmic free Ca2+ concentration in Arabidopsis leaf cells in a similar transient fashion. Physicochemical processes, including interactions with odorant binding proteins and resulting in changes in transmem- brane potentials, can underlie VOCs-mediated signaling processes. However, whether the volatile responses occur in a specific fashion remains to be answered.