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Abstract Detail



Ecological Section

Bowler, Rebecca [1], Fredeen, Arthur L. [2], Massicotte, Hugues B. [2].

Assessing photosynthesis, natural abundance of stable C and N isotopes, and populations following disturbance in putative partial myco-heterotrophic Pyroleae species in central British Columbia.

The vast majority of plant taxa in terrestrial ecosystems form symbiotic relationships between root and mycorrhizal fungi, trading photosynthetic carbon (C) in exchange for water and minerals obtained by fungal hyphae. Hundreds of myco-heterotrophic (MH) species across diverse plant taxa, however, have evolved to exploit the nutrient exchange by deriving some C from mycorrhizal networks. Achlorophyllous plants have long been known to rely on mycorrhizal networks for all of their C but recently some ‘green’ plants have been discovered that obtain C from both autotrophy and myco-heterotrophy. The Ericaceae contains both full MHs (sub-family Monotropoideae) and putative partial MHs (tribe Pyroleae). Many studies assessing and quantifying extent of mycoheterotrophy in plants use natural abundances of stable isotopes of C (12C & 13C) and N (14N & 15N) as a key analytical tool since MH plants have distinct isotopic signatures compared to surrounding autotrophs. Few studies have measured photosynthetic capacity in these plants, however, making interpretation of isotope data somewhat limited. This multi-year project had several purposes: 1) to perform a field manipulation experiment to determine how drought and shade affect MH nutrition; 2) to determine how MH populations were affected by mountain pine beetle mortality and salvage harvesting, and; 3) to summarize photosynthetic and isotopic data over the study period, to apply a novel method to estimate the relative contribution of autotrophic C gains in partial MHs. Of the species investigated, Chimaphila umbellata consistently showed mainly autotrophic C gains and responses to light levels, while Orthilia secunda and Pyrola chlorantha had low inherent photosynthetic rates indicating that up to 30% of C gains were MH. Drought had little effect on myco-heterotrophy during experimentation. Populations of all Pyroleae species were lower in harvested sites compared with residual, post pine beetle forests, especially P. chlorantha. Where individuals occurred in clearcuts, they usually showed reduced vigour, indicative of high light stress and N-deficiency, suggesting lower reliance on mycorrhizal fungi for C than N. With increasing recognition of conservation needs, and the importance and complexity in host-parasite and symbiotic interactions, more research needs to be done to fully understand how these fascinating plants impact forest succession, competition and fitness.


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1 - University of Northern BC, Natural Resources and Environmental Studies graduate program, 3333 University Way, Prince George, BC, V2N 4Z9, Canada
2 - University of Northern BC, Ecosystem Science and Management, Natural Resources and Environmental Studies Institute, 3333 University Way, Prince George, BC, V2N 4Z9, Canada

Keywords:
Partial myco-heterotrophy
Pyroleae
stable isotopes
Photosynthesis
mycorrhizae
two-source mixing model.

Presentation Type: Oral Paper:Papers for Sections
Session: 21
Location: Salon 17/18/The Shaw Conference Centre
Date: Monday, July 27th, 2015
Time: 1:30 PM
Number: 21001
Abstract ID:886
Candidate for Awards:Cinq Mars Award


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