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

Volatile oils were analysed from juvenile and adult leaves collected f rom natural populations of five species from the series Obliquae (Euca lyptus obliqua, E. delegatensis, E regnans, E. sieberi and E pauciflor a) and seven species from the series Piperitae (E. risdonii, E. tenuir amis, E. pulchella, E amygdalina, E. nitida, E. radiata and E. coccife ra) of the informal subgenus Monocalyptus (genus Eucalyptus). Oil yiel ds (1.3-4.9% dry wt.) from adult leaves of all species were markedly h igher than from corresponding juvenile leaves (0.1-3.1% dry wt.). Vola tile leaf oils of most species are rich in alpha- and beta-phellandren e, 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 th at the Tasmanian eucalypt species from series Obliquae are well differ entiated 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 consis tent 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. Resu lts indicated that volatile leaf oils are useful for chemotaxonomic st udies in Eucalyptus.