The sesquiterpene hydrocarbons of maize (Zea mays) form five groups with distinct developmental and organ-specific distributions

Abstract

The sesquiterpene hydrocarbon chemistry of maize (Zea mays) inbred line B73 was analyzed by both direct solvent extraction and headspace sampling. In seedlings, 15 olefinic compounds were identified, and 21 olefins were detected in mature plants after anthesis. Both solvent extracts and collections of headspace terpenes were found to contain the same compounds in the same relative proportions suggesting that there is no selective barrier to release from plants. Approximately 25% of the stored pool was found to be released from young seedlings per hour. The individual sesquiterpenes varied extensively in their abundance among different organs and developmental stages. Compounds could be divided into five different groups such that the members of each group always occur together in the same constant ratios to one another. Each group has a distinct distribution pattern. Group A includes the two dominant compounds, (E)-beta-farnesene and alpha-bergamotene, and appears only after herbivore damage in seedlings, but is constitutively present in the leaves and husks after anthesis. The major compounds of group B, including alpha-copaene, germacrene D and delta-cadinene, were present throughout the seedling but found only in husks of mature plants. The group C compounds, beta-bisabolene and an unknown sesquiterpene olefin, are restricted to the roots. The presence of group D and E compounds was confined to the leaves and husk of mature plants. The complex sesquiterpene mixture of group D is identical to the products formed by the previously identified terpene synthase TPS4, suggesting that each of the four other sesquiterpene hydrocarbon mixtures may also represent the products of a single terpene synthase.