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Title: Nitrogen control of 13C enrichment in heterotrophic organs relative to leaves in a landscape-building desert plant species

A longstanding puzzle in isotope studies of C 3 plant species is that heterotrophic plant organs (e.g., stems, roots, seeds, and fruits) tend to be enriched in 13C compared to the autotrophic organ (leaves) that provides them with photosynthate. Our inability to explain this puzzle suggests key deficiencies in understanding post-photosynthetic metabolic processes. It also limits the effectiveness of applications of stable carbon isotope analyses in a variety of scientific disciplines ranging from plant physiology to global carbon cycle studies. To gain insight into this puzzle, we excavated whole plant architectures of Nitraria tangutorum Bobrov, a C 3 species that has an exceptional capability of fixing sands and building sand dunes, in two deserts in northwestern China. We systematically and simultaneously measured carbon isotope ratios and nitrogen and phosphorous contents of different parts of the excavated plants. We also determined the seasonal variations in leaf carbon isotope ratios on nearby intact plants of N. tangutorum. We found, for the first time, that higher nitrogen contents in heterotrophic organs were significantly correlated with increased heterotrophic 13C enrichment compared to leaves. However, phosphorous contents had no effect on the enrichment. In addition, new leaves had carbon isotope ratios similar to roots butmore » were progressively depleted in 13C as they matured. We concluded that a nitrogen-mediated process, probably the refixation of respiratory CO 2 by phosphoenolpyruvate (PEP) carboxylase, was responsible for the differences in 13C enrichment among different heterotrophic organs while processes within leaves or during phloem loading may contribute to the overall autotrophic – heterotrophic difference in carbon isotope compositions.« less
 [1] ;  [2] ;  [3] ;  [3] ;  [4] ;  [3] ;  [3] ;  [3] ;  [3] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [3] ;  [3] ;  [6]
  1. Chinese Academy of Forestry, Beijing (China). Inst. of Desertification Studies and Research Inst. of Forestry
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Div. and Climate Change Science Inst.
  3. Chinese Academy of Forestry, Beijing (China). Inst. of Desertification Studies
  4. Chinese Academy of Forestry, Beijing (China). The Experimental Center of Desert Forestry, Dengkou (China)
  5. Tsinghua Univ., Beijing (China). Center for Earth System Science
  6. Chinese Academy of Forestry, Beijing (China)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Biogeosciences Discussions (Online)
Additional Journal Information:
Journal Name: Biogeosciences Discussions (Online); Journal Volume: 11; Journal Issue: 9; Journal ID: ISSN 1810-6285
European Geosciences Union
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States