School of Plant Biology

Jeremy Bougoure

Thesis

The role of mycorrhizal fungi in nutrient supply and habitat specificity of the rare myco-heterotrophic underground orchid, Rhizanthella gardneri Rogers

Summary

The underground orchid (Rhizanthella gardneri) is a fully subterranean myco-heterotrophic plant limited to two known locations in southern Western Australia.

This orchid is unable to photosynthesise and shows strong mycorrhizal colonisation, and it is assumed that R. gardneri relies on a fungal partner to supply carbohydrates and other nutrients. The fungus interacting with R. gardneri is also thought to form ectomycorrhizas with the shrub Melaleuca uncinata, resulting in a tripartite association.

My research is focused on understanding and quantifying nitrogen and carbon transfer processes within this tripartite association. I am using glasshouse experiments in conjunction with field studies to establish if and how mycorrhizal fungi and M. uncinata supply R. gardneri with minerals and energy.

Methods include isotopic labelling of nutrients and carbon (15N and 13C), and tracking nutrient transfers from fungi to roots using NanoSIMS.

Why my research is important

The underground orchid is a critically endangered species limited to highly fragmented and disturbed reserves within the central Wheatbelt and southern coast of Western Australia.

These reserves have been monitored for the past 20 years, and there have been significant declines in R. gardneri population and general habitat ‘health’. In 2004, surveys reported only a single flowering plant in one population (central Wheatbelt) and approximately 50 plants at the other (southern coast).

My research is important for the long term survival of R. gardneri as it provides essential knowledge in relation to its basic biology and how it functions within its habitat, including its supposed dependency on other plants and fungi.

This knowledge will be used to maintain and improve existing habitat health, locate new populations and in future translocation attempts.

Funding

• This project is funded by the Australian Research Council (LP0454276) in collaboration with the WA Department of Conservation and Land Management. Additional funding is also supplied by the World Wildlife Fund (WWF).