VARIATION IN VOLATILE LEAF OILS OF THE TASMANIAN EUCALYPTUS SPECIES .1. SUBGENUS MONOCALYPTUS

Volatile oils were analysed from juvenile and adult leaves collected from natural populations of five species from the series Obliquae (Eucalyptus obliqua, E. delegatensis, E regnans, E. sieberi and E pauciflora) and seven species from the series Piperitae (E. risdonii, E. tenuiramis, E. pulchella, E amygdalina, E. nitida, E. radiata and E. coccifera) of the informal subgenus Monocalyptus (genus Eucalyptus). Oil yields (1.3-4.9% dry wt.) from adult leaves of all species were markedly higher than from corresponding juvenile leaves (0.1-3.1% dry wt.). Volatile leaf oils of most species are rich in alpha- and beta-phellandrene, cis- and trans menth-2-en-1-ol, while some were rich in 1,8-cineole or alpha, beta and gamma-eudesmol. Multivariate analyses indicated that the Tasmanian eucalypt species from series Obliquae are well differentiated and exhibit little intraspecific variation in percentage oil composition. In contrast, species from the series Piperitae show great intraspecific variation and are poorly differentiated which is consistent with morphological studies. The chemical composition of Volatile oils of juvenile and adult leaves were qualitatively similar but were quantitatively different in some oil components for some species. Results indicated that volatile leaf oils are useful for chemotaxonomic studies in Eucalyptus.