Headspace GC-MS analysis of differences in intra- and interspecific Terpene profiles of Picea pungens Engelm. and P. abies (L.) Karst

Abstract

Conifer terpenes mediate a number of ecological roles such as deterring herbivory and allelopathic (plant-plant) communication. These terpenes also effect air quality and climate models and are used in chemotaxonomic studies. Herein we report on variation in both intra- and interspecific spruce terpenes using static headspace gas chromatography mass spectrometry (HS-GC-MS) and principal component analysis (PCA) of ‘fingerprint’ volatile profiles. Samples of blue spruce (Picea pungens), Norway spruce (P. abies), and cedar of Lebanon (Cedrus libani), an outgroup control, were analyzed by HS-GC-MS using both chiral and achiral GC columns. Headspace sampling parameters, temperature and heating time, were optimized to maximize detected terpenes. PCA of terpene ‘fingerprint’ profiles showed differences by species, by individual trees, but perhaps surprisingly not by environmental conditions. Analysis of blue and Norway spruce over several months show that volatile emissions remained remarkably constant unlike cedar of Lebanon, which showed a much greater variation in volatile profiles. Branches and buds from both spruces were found to release greater amounts of terpenes than samples of needles. The enantiomeric compositions of seven chiral monoterpenes were found to be largely similar between the three conifers with the exception of (−)-α-pinene, which was the dominant enantiomer released by Norway spruce and cedar of Lebanon, while (+)-α-pinene slightly predominated in blue spruce. While not the primary focus of this work, we believe this constitutes the first report on the enantiomeric composition of terpenes in cedar of Lebanon.