Chemotaxonomy according to leaf terpenes of eight cypress species growing in the Czech Republic in the light of modern phylogenetic classification

There have been many attempts to create a systematic arrangement of gymnosperms confirming the phylogenetic relationships among extant plants. Chemical data obtained by analysing leaf terpenes by gas chromatography have been used to study the chemotaxonomic characters of cypress species in an attempt to support modern phylogenetic classification. While the dominant terpenes proved to be reliable distinguishing features at the individual level of species, the relative proportions of individual terpene fractions were a significant feature distinguishing individual cypress genera. The Juniperus and Sabina genera were characterized by the highest content of monoterpenes (Sabina virginiana up to 95%). Genus Juniperus also contained higher amounts of sesquiterpenes (e.g. hedycaryol) and diterpenes (e.g. totarol), but genus Sabina showed a negligible content of these terpene fractions. Genus Xanthocyparis showed the highest content of diterpenes (up to 59%) of all species studied here, but a lower content of monoterpenes and sesquiterpenes. Genus Chamaecyparis was characterized by balanced amounts of mono- and sesquiterpenes and also by a higher content of diterpenes (e.g. beyerene, totarol). Although genus Taxodium is from the Taxodioideae subfamily, it showed a terpene fractions content very similar to that of genus Juniperus from the subfamily Cupressoideae. Chemical data proved to be a reliable biomarker corresponding to the phylogenetic classification of conifers. No significant effect of seasonality on leaf terpenes production was proved in a study over a period of 6 years, with exception of the Sabina pfitzeriana and Chamaecyparis lawsoniana species. Slight differences were revealed among individual seasons.