Dear Editor,Monoterpenes,together with sesquiterpenes,play varying roles in plant interactions with the environment depending on the organs in which they are produced;these compounds likely function to attract pollinators when they are present in flowers and can protect plants against herbivores or microbes when produced in leaves or in roots.It is well known that geranyl diphosphate (GPP),the common precursor of monoterpenes,is biosynthesized by geranyl diphosphate synthase (GPPS).