A comparison of the volatile oils of mature versus young leaves of Juniperus scopulorum: Chemosystematic significance

The volatile oils of leaves of clonal, greenhouse grown trees of J. scopulorum cv. platinum were examined from young (juvenile or whip leaves) and mature (adult or scale leaves) foliage. Of 36 compounds subjected to analysis of variance, 19 showed significant differences between young and old leaves. In general, the hydrocarbon terpenoids were higher in concentration in new leaves while the oxygenated compounds were higher in the older leaves. This same pattern has been reported in several other gymnosperms. Numerical taxonomy using data on the volatile oils from young and mature leaves yielded the same relative similarities among the five trees examined. Surprisingly, the plants were more similar in the volatile oil from the young leaves than from the mature leaves. The mixing of different ages of leaves in samples for chemosystematic studies is, however, to be discouraged