Characterisation of volatile constituents of six native New Zealand ferns and changes in volatile emission in response to herbivore, mechanical wounding and phytohormone treatments : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Manawatū Campus, New Zealand
Evolution has led to the development of countless defence strategies in terrestrial plants to deal with the threat of herbivory and disease. The production of specialised morphological structures, such as thorns and trichomes, is a prominent defence mechanism that directly deters potential herbivores. However, plants are capable of enlisting the aid of natural predators and parasites of attacking herbivores as a means of indirect defence, through the production and release of volatile organic compounds. This has prompted much research into the regulation and ecological roles of volatile organic compounds in many higher plant groups. However, similar studies are seldom in lower plants such as the Monilophytes thus we know very little concerning the ecological importance of plant emitted volatiles in this group. In this study, I investigated the volatile compounds released by six abundant native fern species using direct solvent extraction and headspace collections, and characterized the volatile emissions under natural herbivory, phytohormone treatment, and mechanically induced stress. Solvent extracts and headspace collections were analysed using gas chromatography coupled with mass spectrometry allowing the quantitative and qualitative description of the volatile profiles. These results were then used to relate volatile emission to the growth mode and other potential defence strategies of these species. A total of 15 volatile compounds were identified over the course of this thesis with links to fern physiology. Quantitative results revealed no differences in emissions under phytohormone treatment or artificially induced stress. The comparison of two methods, solvent extraction and headspace sampling, reveals the limitations the solvent extraction method has on elucidating fern-insect interactions. Research on fern volatiles could give insight into the evolution of anti-herbivore defence mechanisms in plants and the interactions between native ferns and arthropod communities. Potential applications of research in fern chemistry include pharmaceutical or perfumery uses and fern conservation, which should be incentives for further work. The results and conclusions made from this thesis does not only contribute to the limited pool of knowledge in this field of research but may also serve as a foundation for future studies.