Epicuticular wax of juvenile Eucalyptus leaves and headspace analysis of leaf volatiles

This study was performed to determine the variation in leaf epicuticular wa x composition and yield between 17 species of Eucalyptus with horticultural potential, and to identify a possible solvent for epicuticular wax using h eadspace volatile analysis. Variation in the amount and composition of leaf epicuticular wax among 17 species of Eucalyptus L'Heritier (Myrtaceae) wit h horticultural potential, was characterized by GC, TLC and GC/MS. Across s pecies, was yield ranged from 0.7 to 4.5 mg/cm(2). The major wax constituen ts in a II species except E. delegatensis R. Baker, were beta-diketones (24 .7-83.0%), followed by wax eaters (6.4-26.5%), n-alkanes (3.5-26.5%), fatty acids (3-15.9%), n-alcohols (0.6-11.1%) and aldehydes (0-9.2%). In E, dele gatensis the major wax constituents were wax eaters (46.6%), beta-diketones (24.7%), n-alkanes (11.5%), fatty acids (7.5%), n-alcohols (5.2%) and alde hydes (4.3%). Volatile organic compounds emitted from developing Eucalyptus leaves of six species were studied using solid phase microextraction (SPME ), and were analyzed by GC and GC/MS. Leaf oils were extracted from four of the six species and the relative amounts of volatile compounds in the extr act and headspace compared. The major volatile constituents were cc-pinene (11.4-57.8%) headspace; 15.3-32.2%, oil extract) and 1,8-cineole (3.2-88.6% , headspace; 20.8-54.7% oil extract). Other terpenoids present in the heads pace in significant quantities were allo-aromadendrene, viridiflorene, alph a-thujene, alpha-phellandrene, gamma-terpinene and limonene. In the oil ext ract, allo-aromadendrene, alpha-phellandrene, viridiflorene and limonene we re present in significant quantities. Components of leaf oils are potential solvents involved in the transport of waxes from the epidermis to the cuti cle, although this is not confirmed by the present study.