title: Isotopic evidence of partial mycoheterotrophy in the Gentianaceae: Bartonia virginica and Obolaria virginica as case studies.
abstract: OBJECTIVE
  An estimated 10% of plant species have evolved to steal C from their symbiotic fungal partners (mycoheterotrophy), and while physiological evidence for full and partial mycoheterotrophy is well developed in the Orchidaceae and Ericaceae, it is lacking for the majority of other mycoheterotrophic taxa. The family Gentianaceae not only contains several lineages of achlorophyllous mycoheterotrophs, but also contains species that are putative partially mycoheterotrophic. The North American genera Bartonia and Obolaria (Gentianaceae) are green but have leaves reduced to scales or foliose bracts and so have ambiguous mycoheterotrophic status. •
  
  
  METHODS
  We investigated the natural abundance (13)C and (15)N profiles of both genera along with total N and chlorophyll content and investigated mycorrhizal infection using light microscopy. •
  
  
  RESULTS
  The shoots of B. virginica were significantly more enriched in (15)N than the surrounding vegetation but not in (13)C. In contrast, the shoots of O. virginica are not enriched in (15)N compared to the surrounding vegetation but were significantly enriched in (13)C. Total N concentrations were significantly higher than the surrounding vegetation in B. virginica, while the collaroid roots of both species were infected by arbuscular mycorrhizal fungi. •
  
  
  CONCLUSIONS
  This microscopic evidence coupled with the natural abundance stable isotope profiles strongly suggests that both species are partially mycoheterotrophic. However, differences in the root-shoot stable isotopic patterns relative to surrounding vegetation between B. virginica and O. virginica are suggestive of the utilization of different physiological pathways or extent of commitment to mycoheterotrophic C gain.
authors: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, South Yorkshire, S10 2TN, UK.
authors: Duncan D
authors: DD
authors: Cameron
authors: Jay F
authors: JF
authors: Bolin