Supervisor: Mark Clements
Background
Australia has a diverse range of orchids with about 1100 species described. Approximately 20 % of these are listed by Environment Australia as threatened. Orchids are of considerable interest for several reasons. First, it is the most speciose plant family in the world (c. 30,000 species). Second, within the family, a broad range of pollination systems has evolved, and as a consequence their flower morphology is extremely diverse. In addition, partly because of the wide variety of attractive floral displays, many people culture orchids and therefore they are commercially important.
All orchids have small seeds and depend on mycorrhizal fungi for germination in nature. Increasing the ability to germinate orchid seeds is an important research topic because it is central to the propagation of orchids for cultivation and for conservation of endangered species, including the possible re-introduction of seedlings back into suitable natural habitats. There are two ways to propagate orchids by seed: 1) asymbiotic germination, using culturing media with nutrients for developing seeds; and 2) symbiotic germination, using orchid mycorrhizal fungi. For conservation purposes it is very important to determine the most appropriate fungi to stimulate seed germination and development of each orchid species. A major research question is whether endangered species interact specifically with particular groups of mycorrhizal fungi or whether all fungi are equally effective at promoting germination.
The long term storage (LTS) of germ plasma in the form of seeds is generally considered to be one of the best means of conserving species, in particular those listed as threatened. However, orchid seeds are unique in flowering plants in that they lack an endosperm. Instead the seed comprises only an undifferentiated embryo surrounded by a seed coat. Cells in the embryo contain lipids that are used as the energy source. While seeds of many species of orchids have been kept in LTS, it is still not clear whether this procedure is appropriate, and how long seeds can survive under these conditions.
Research project
In the first part of this project we aim to answer the following questions: 1) Do seeds of endangered Pterostylis species (e.g. P. gibbosa) germinate and develop faster with mycorrhizal fungi than with asymbiotic cultural medium? 2) Are these species specific in their mycorrhizal fungi requirement? 3) Which is the best fungus at inducing germination and seedling growth in these species?
The CPBR has a collection of seeds of orchids, including some endangered species, which are kept in LTS. In the second part of the project we aim to test whether LTS significantly affects seed viability and determine if it is an appropriate technique for conservation of these species. In order to answer these questions a series of seed germination experiments will be developed. Fresh seeds and those in LTS of endangered Pterostylis species will be sown on both commercial cultural media and media with different mycorrhizal fungi for germination. Germination and development will be recorded and analyzed statistically.
In carrying out this project, the student will be participating in a broader long-term project with significant conservation implications for endangered Australian orchids. The student will have the opportunity to undertake field trips to collect orchid seeds and will learn how to culture and use fungi for orchid seed propagation. A major part of the project will involve designing, carrying out and analysing the laboratory and glasshouse experiments.