Eucalyptus, Melaleuca alternifolia, Research Updates|

The importance of proper sampling and methods of ensuring it are discussed. An investigation was made on variations of oil yield with age of leaf for Eucalyptus spp. For E. dives yields varied from 4.0%. for aged to 9.6%. for young leaves, and for E. australiana from 3.8 to 7.0% and in another series from 5.8 to 10.1%, while for E. smithii there was no significant difference between old and young leaves, the leaves of this species being coated with a wax-like film which may prevent loss of oil by volatilization. Similar investigations were made on variation in oil composition. Samples of oil from leaves of different ages from two trees of E. dives were analysed for their content of phellandrene, which varied from 14% for aged to 24 % for young leaves. There was no significant difference in total phellandrene content between the two trees, or in that of leaves of the same age from them. Similar results were obtained from E. australiana; phellandrene was absent from a number of older leaf age groups. The cineol content for E. australiana was not significantly different for the different leaf groups but yield dropped with age; E. smithii showed a pronounced rise in cineol content in the older leaves, but yield remained constant. Studies to determine the variation of oil yield and composition were made on two physiological forms, E. dives var. ‘C’ and E. dives type. In the former, yield of oil varied from 1.5 to 5.6% and the cineol content of the oil from 4.6 to 7.0%. Nine of the 5O trees studied contained phellandrene in amounts varying from 4 to 9 %. In the type, oil yields varied from 2 to 4.6% on a fresh-weight basis. The piperitone content varied from 35.0 to 53.O% and that of phellandrene from 13.0 to 32.0% Preliminary studies on a few samples (40 and 30 respectively) of Melaleuca alternifolia and Leptospermum citratum showed for L. citratum oil yields of 3.4-6.0 % with 53-85 % total aldehyde content, and for M. alternifolia yields of 4.5-10.4% and cineol contents ranging from 7 to 64%; in 3 distinct series, 7-15%, 31-40% and 54-64%. Unfortunately, the highest yielders did not possess the best oils. [Cf. For. Abstr. 11 (Nos. 2184-7; 3186-7); 12 (Nos. 1502-4, 3301-3). KEYWORDS: Eucalyptus australiana \ Eucalyptus dives \ Eucalyptus smithii \ Leptospermum citratum \ Melaleuca alternifolia \ Oils taxonomic value \ variation.

Reference: Bryant, L. (1950). “Variations in oil yield and oil composition in some species of Eucalypts and Tea trees.” Technical Notes. Forestry Commission (Division of Wood Technology), New South Wales 4(Spec. Issue): 6-10.

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