Leaf epicuticular waxes in the taxonomy of the Epacridaceae

Leaf epicuticular waxes have been studied in the plant family Epacridaceae from a primarily taxonomic aspect. Both the form of the wax and its chemical composition have been analysed. Wax morphology in approximately 95% of the known species from 30 of the 31 recorded genera has been examined by scanning electron microscopy (SEM). Two wax categories, amorphous and structured including four structured wax types are recognised. Distribution and variation in wax types has relevance at all levels of the taxonomic hierarchy. In a representative number of species (74) from 25 genera (covering the variation in wax types recognised from the SEM survey), complete chemical composition of the waxes has been undertaken using GC-MS. Quantitative measurements of individual components are based upon integrated peak areas. Compared with most previous reports the current study has obtained very satisfactory results from direct analysis of the crude wax, significantly reducing both preparation and analysis time for each species. The results indicate that wax structure is correlated with chemical composition and that the distribution of wax components within the family and their relative proportions between genera and species has taxonomic importance. In the final section of the thesis a taxonomic reassessment of the genus Cyathodes in Australia and New Zealand is reported incorporating data from all available sources. Chemical data, including waxes, contributes valuable additional information to the traditional morphologically based data and assists in the clarification of taxonomic problems within the genus.