PARENT SESSION
Poster Session # 15: Plant Ecology.

Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Respiratory CO₂ is ¹³C-enriched in five C3 plants.

Xu, Chengyuan^{*,1, 2}, Lin, Guanghui¹, Griffin, Kevin ², Sambrotto, Raymond², ¹ Biosphere 2 Center of Columbia University, Oracle, AZ² Lamont Doherty Earth Observatory of Columbia University, Palisade, NY

ABSTRACT- We compared the carbon isotope ratios between respiratory CO₂ and leaf organic components (soluble sugar, water soluble fraction, starch, protein and bulk organic matter) in 5 C3 plants grown in green house and Biosphere 2, including one species, Populus deltoides, in 3 different growth CO₂ concentrations. For all species or CO₂ treatments, respiratory CO₂ was ¹³C-enriched in comparison with all leaf organic components, but the amount of enrichment does not depend on the signature of the organic components examined. We also found that ¹³C of leaf organic components are correlated to ¹³C of leaf respiratory CO₂. The amount of ¹³C enrichment was significantly influenced by the type of organic component examined, but not by species or CO₂ treatments. We argue that in normal growth condition, non-statistical carbon isotope distribution in sugar may determine the signature of respiratory CO₂ dominantly. These results suggest that 1) ¹³C-enriched respiratory CO₂ is widespread in C3 plants and 2) we can predict ¹³C of respiratory CO₂ for ecosystem scale study by combining the average ¹³C-enrichment in respiratory CO₂ and the signatures of leaf organic components.

Key words: carbon isotope fractionation, dark respiration, keeling plot