|Kate Levendosky - Plant
University of Maryland - Baltimore County, Catonsville, MD
Uncovering the Hidden Links between an Orchid, its Fungi
and Ectomycorrhizal Trees:
ecology and distribution of Corallorhiza
This summer found me running gels in the lab, sitting on the forest floor searching for 4cm tall orchid shoots, generating maps at a computer, or looking at fungi through a microscope. My internship in the Plant Ecology lab at SERC focused on examining the spatial distribution of a local orchid (Corallorhiza odontorhiza), the fungi that the orchid associates with and the trees that the fungi form ectomycorrhizas with.
All orchids produce incredibly tiny seeds that are perfect for wind dispersal but that do not contain sufficient energy reserves to enable the orchid to grow and develop on its own. Therefore, all orchids must form associations with fungi in order to have the energy to get through the first stages of their life. While this is a requirement of all orchids, Corallorhiza odontorhiza is one of a group of orchids that are essentially non-photosynthetic and thus rely on fungal associations throughout their life.
While many mycorrhizal associations are characterized as symbiotic relationships between soil fungi and plant roots (with the host plant receiving minerals and nutrients from the fungi and the fungi receiving fixed carbon from the plant), there is no evidence that orchids give anything back to their fungal associates. This lack of reciprocation by the orchids has led some to classify orchids as parasites. Corallorhiza odontorhiza actually takes this parasitism a step further by associating with fungi that form ectomycorrhizas with trees.
During the course of my internship I had a couple of goals. First, I wanted to map the distribution of Corallorhiza odontorhiza in a 50x80m plot at SERC where it has been occurring consistently for at least 8 years. Second, I wanted to examine the spatial distribution of the fungi that associate with Corallorhiza odontorhiza within the orchid plot. Third, I wanted to examine the ECM tree roots adjacent to Corallorhiza to determine if they contain the Corallorhiza fungi.
The initial results of my study suggest that the locations of the Corallorhiza plants are correlated from year to year. I also found that the fungal individuals that associate with Corallorhiza plants may be between 0.1-1m in diameter and that there are probably multiple species of fungi in the Corallorhiza plot. My results also showed that Corallorhiza fungi are present in some ECM tree roots.My internship at SERC has been an incredibly rewarding and educational experience. My understanding of molecular methods has increased exponentially over the summer and I have developed a deep appreciation for the influence of soil fungi on the spatial distribution of vegetation. As I recently graduated from UMBC with a degree in Geography and Environmental Systems, I plan to participate in a few more internships before attending graduate school in geography or ecology.
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