Respiratory carbon metabolism in the high mountain plant species Ranunculus glacialis
Very little is known about the primary carbon metabolism of the high mountain plant Ranunculus glacialis . It is a species with C 3 photosynthesis, but with exceptionally high malate content in its leaves, the biological significance of which remains unclear. 13C/12C-isotope ratio mass spectrometry...
| Published in: | Journal of Experimental Botany |
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| Main Authors: | , , , , , , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
2006
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| Subjects: | |
| Online Access: | http://jxb.oxfordjournals.org/cgi/content/short/erl149v1 https://doi.org/10.1093/jxb/erl149 |
| Summary: | Very little is known about the primary carbon metabolism of the high mountain plant Ranunculus glacialis . It is a species with C 3 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 Q 10 of 2, and the respiratory quotient (CO 2 produced divided by O 2 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 CO 2 fixed by photosynthesis was labelled, little labelling of the CO 2 subsequently respired in the dark was detected, indicating that: (i) most of the carbon recently assimilated during photosynthesis is not respired in the dark; and (ii) the carbon used for respiration originates from (unlabelled) reserves. This is the first demonstration of such a low metabolic coupling of assimilated and respired carbon in leaves. The biological significance of the uncoupling between assimilation and respiration is discussed. |
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