Collaborative Research: Orchid-Fungal Interactions-A System for Testing Hypotheses about the Ecological Role and Distribution of Mycorrhizal Fungi in Affecting Plant Distribution

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All terrestrial orchids require symbiotic fungi called mycorrhizae and can persist only when these fungi are present. They interact with a wide range of fungi - some orchids are extreme specialists, while others are generalists that can host many different fungi. The proposed study uses orchid-mycorrhizal associations as a model system to investigate the roles of symbiotic fungi and of the chemical composition of the substrate in regulating the distribution and growth of orchid host plants. To determine whether symbiotic fungi regulate the distribution of orchids, a series of laboratory and field experiments is proposed in which orchid seeds, fungal partners, litter substrates and abiotic factors (light, water) are manipulated. To determine how substrate quality affects orchid growth, carbon sources for seedling orchids will be determined under varying substrate, water and light regimes. This study will contribute fundamental knowledge about orchid-mycorrhizal interactions and about the nature of nutrient (carbon) acquisition under different stress (substrate quality, light, water) regimes. Results from this study research will substantially benefit conservation efforts. All three of the institutions involved in the project will include undergraduate students in research, and intern activities at the Smithsonian Institution that focus on minority institutions will be used to solicit student participation in the study.