Respiratory carbon metabolism in the high mountain plant species Ranunculus glacialis
Very little is known about the primary carbon metabo-lism of the high mountain plant Ranunculus glacialis. It is a species with C3 photosynthesis, but with exceptionally high malate content in its leaves, the biological significance of which remains unclear. 13C/12C-isotope ratio mass spectrometry (...
| Main Authors: | , , , , , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
2006
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| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.571.9947 http://jxb.oxfordjournals.org/content/57/14/3837.full.pdf |
| Summary: | Very little is known about the primary carbon metabo-lism of the high mountain plant Ranunculus glacialis. It is a species with C3 photosynthesis, but with exceptionally high malate content in its leaves, the biological significance of which remains unclear. 13C/12C-isotope ratio mass spectrometry (IRMS) and 13C-nuclear magnetic resonance (NMR) labelling were used to study the carbon metabolism of R. glacialis, paying special attention to respiration. Although leaf dark respiration was high, the temperature response had a Q10 of 2, and the respiratory quotient (CO2 produced divided by O2 consumed) was nearly 1, indicating that the respiratory pool is comprised of carbohydrates. Malate, which may be a large carbon substrate, was not respired. However, when CO2 fixed by photosynthesis was labelled, little labelling of the CO2 subsequently respired in the dark was detected, indicating that: (i) most of the carbon recently assim-ilated during photosynthesis is not respired in the dark; and (ii) the carbon used for respiration originates from (unlabelled) reserves. This is the first demonstra-tion of such a low metabolic coupling of assimilated and respired carbon in leaves. The biological signifi-cance of the uncoupling between assimilation and respiration is discussed. |
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