Recipient Organization
STATE UNIV OF NEW YORK
(N/A)
SYRACUSE,NY 13210
Performing Department
Environmental & Forest Biology
Non Technical Summary
Epipactis helleborine (L.) Crantz (broad-leaved helleborine) is an orchid native to Europe that was first discovered in North America in Syracuse, New York in 1879 (Correll, 1978). Since then it has become naturalized, growing in a variety of habitats such as forest understories and urban settings, and in some areas so widely that it is considered a weed (Kolanowska, 2013; Tenney, 2016). Like other orchids, E. helleborine initially relies upon mycorrhizal fungi for germination, and adult E. helleborine plants continue to support their photosynthesis with carbon acquired from their mycorrhizal fungi (Bidartondo et al., 2004). Partial parasitism of mycorrhizal fungi by orchids is termed mixotrophy to denote the combination of autotrophic and myco-heterotrophic (i.e., a consumer of fungi) nutrition (Julou et al., 2005). This strategy likely helps to mitigate low light when growing in forest understories and may have contributed to E. helleborine's naturalization (Bidartondo et al., 2004). Mixotrophic orchids may also exert a degree of control over their nutrition source (Gonneau et al., 2014). My research will investigate the hypothesis that E. helleborine has a greater reliance upon its fungi in shadier environments where photosynthesis is limited. This research will elucidate the nutrient dynamics of orchids growing in forest understories and the adaptations they utilize to be successful.The relationship between E. helleborine and its mycorrhizal fungi leans strongly towards parasitism, with the orchid acquiring both carbon and mineral nutrients such as phosphorous and nitrogen from its fungi (Gebauer & Meyer, 2003). This is unlike many other plants which instead are sources of carbon for their mycorrhizal fungi, in what is generally viewed as a mutually beneficial relationship (Johnson et al., 1997). As a facultative parasite, E. helleborine subverts the normal mycorrhizal symbiosis, stealing carbon from fungi while still photosynthesizing. Since the mycorrhizal fungi that E. helleborine parasitizes are fully heterotrophic, a tripartite relationship is formed between the orchid, mycorrhizal fungus, and autotrophic host, e.g. a tree, which supplies carbon to the fungus (Gebauer & Meyer, 2003; Bidartondo et al., 2004). Preliminary data in New York suggest that E. helleborine associates with Tuber species, better known as truffles (Thomas Horton, unpublished data). Other studies have also identified Ascomycetes (species in Tuber and Wilcoxina) and Heterobasidiomycetes (species in Ceratobasdium and Sebacina) as mycorrhizal symbionts in New York (Bidartondo et al., 2004). However, the diversity of E. helleborine's mycorrhizal symbionts warrants further investigation, as E. helleborine's success in North America may be due to its association with a broad range of fungi in addition to its mixotrophic nutrition.It is surprising that E. helleborine has become so extensively established given that its germinating seeds are obligate myco-heterotrophs (Arditti & Ghani, 2000). However, there is strong evidence that mycorrhizal fungi play a role in facilitating the invasion of plants in other systems, e.g a pine invasion enabled by the mycorrhizal fungus Suillus luteus (Hayward et al., 2015). In the case of orchids, it is possible that low specificity towards mycorrhizal fungi would make naturalization more likely, as the orchid would have less biological controls on its germination and growth (Bidartondo & Read, 2008). Specifically, mycorrhizal fungi may have helped to facilitate E. helleborine's naturalization via a supply of carbon to establishing seedlings (Bidartondo & Read, 2008). Conversely, if E. helleborine exhibits high fidelity to a group of specific fungi, this would limit E. helleborine's invasion to locations where those fungal species are well established (Bidartondo & Read, 2008). The most prevalent examples of high mycorrhizal specificity are fully myco-heterotrophic plants, for example the chlorophyll-lacking Monotropa uniflora (Bidartondo & Bruns, 2001). Therefore, it is more likely that as a mixotroph E. helleborine parasitizes several different mycorrhizal fungi, considerably broadening its range.By investigating the diversity of mycorrhizal fungi associated with E. helleborine, I will provide insights into why this orchid has been so successful at invading a variety of habitats. Furthermore, because E. helleborine's mixotrophic strategy likely contributes to its broad habitat, I will also assess E. helleborine's nutritional budget in different habitats to explore to what extent it concurrently utilizes photosynthesis with parasitism of fungi to augment its carbon needs. This will contribute to a greater understanding of the ecology of orchids in forest understories, and the nutritional strategies that they have evolved to mitigate the effects of low light. I will investigate the following objectives during my research:Objective 1: Determine how the photosynthetic capability of E. helleborine individuals varies over a growing season.Objective 2: Compare carbon budgets of populations in different light conditions.Objective 3: Experimentally manipulate light availability in an attempt to induce E. helleborine individuals to develop a greater reliance upon mycorrhizal fungi for carbon, as assessed by quantification of mycorrhizal colonization and stable isotope analyses.Objective 4: Collect root samples for quantification and identification of mycorrhizal fungi to compare fungal diversity between site.I hypothesize that early in the growing season E. helleborine will have low photosynthetic capability and thus higher reliance on its mycorrhizal fungi compared to when leaves are more fully developed (Objective 1). This will be evidenced by stable isotope analysis indicating that the percent carbon and nitrogen that E. helleborine recovers from its mycorrhizal fungi. Similarly, populations of E. helleborine individuals that grow in more shaded habitats will photosynthesize less (i.e. parasitize mycorrhizal fungi more) than E. helleborine individuals receiving higher irradiance (Objective 2). Shading E. helleborine plants will cause E. helleborine plants in the manipulated condition to require more carbon from their mycorrhizal fungi due to a reduction in photosynthetic efficiency (Objective 3). Lastly, I expect that the mycorrhizal fungi identified from E. helleborine roots will belong to a diverse group of fungi and that the communities of fungi associated with E. helleborine will differ between sites (Objective 4).Awarded Start Date: 6/1/19Sponsor: Multiple Sponsors
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
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Project Methods
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