Pine species are usually classified to morphologically distinct and taxonomically typified taxa. Nevertheless, a large number of hybrids have evolved as a result of introgressive hybridisation. The individual morpho-anatomical characteristics of these hybrids in several cases can be deceiving and can lead to wrong assignment to typified taxa.
The high degree of genotypic variability observed in a number of Pinus species is reflected in the biochemical variability, which is usually studied at the levels of terpene composition and isoenzyme variation.
In the framework of our chemical and biological investigations on the volatile metabolites of Greek endemic and Mediterranean conifers (Roussis et al., 1999; Petrakis and Roussis, 1997) we had the opportunity to study the composition of the volatile metabolites from the needle essential oils of 178 Pine trees belonging to the 10 most abundant Pinus species (Pinus halepensis, P. brutia, P. canariensis, P. pinea, P. nigra, P. pinaster, P. peuce, P. radiata, P. attenuata and P. heldreichii) and growing in Greece in natural habitats.
The essential oils were analysed by GC and GC-MS and the identification of the chemical constituents was based on comparison of their Rts and mass spectra with those obtained from authentic samples and/or libraries spectra. Forty-nine metabolites, constituting the majority of the volatile metabolites, were identified and quantified. The majority of the identified metabolites were found to be monoterpenes and sesquiterpenes.
On the basis of the major terpene metabolites, distinct and characteristic chemotypes were assigned for the 10 investigated Pine species. Among the metabolites with the highest discriminate value were a-, b-pinene, limonene, myrcene, E-caryophyllene and germacrene D. Statistical analyses of the chemical and morphoanatomical characters of the investigated trees produced broadly similar classifications for the studied Pinus species.