Document Detail

C4 photosynthetic isotope exchange in NAD-ME- and NADP-ME-type grasses.
MedLine Citation:
PMID:  18375608     Owner:  NLM     Status:  MEDLINE    
Monitoring photosynthetic isotope exchange is an important tool for predicting the influence of plant communities on the global carbon cycle in response to climate change. C(4) grasses play an important role in the global carbon cycle, but their contribution to the isotopic composition of atmospheric CO(2) is not well understood. Instantaneous measurements of (13)CO(2) (Delta(13)C) and C(18)OO (Delta(18)O) isotope exchange in five NAD-ME and seven NADP-ME C(4) grasses have been conducted to investigate the difference in photosynthetic CO(2) isotopic fractionation in these subgroups. As previously reported, the isotope composition of the leaf material (delta(13)C) was depleted in (13)C in the NAD-ME compared with the NADP-ME grasses. However, Delta(13)C was not different between subtypes at high light, and, although Delta(13)C increased at low light, it did so similarly in both subtypes. This suggests that differences in leaf delta(13)C between the C(4) subtypes are not caused by photosynthetic isotope fractionation and leaf delta(13)C is not a good indicator of bundle sheath leakiness. Additionally, low carbonic anhydrase (CA) in C(4) grasses may influences Delta(13)C and should be considered when estimating the contribution of C(4) grasses to the global isotopic signature of atmospheric CO(2). It was found that measured Delta(18)O values were lower than those predicted from leaf CA activities and Delta(18)O was similar in all species measured. The Delta(18)O in these C(4) grasses is similar to low Delta(18)O previously measured in C(4) dicots which contain 2.5 times the leaf CA activity, suggesting that leaf CA activity is not a predictor of Delta(18)O in C(4) plants.
Asaph B Cousins; Murray R Badger; Susanne von Caemmerer
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-03-28
Journal Detail:
Title:  Journal of experimental botany     Volume:  59     ISSN:  1460-2431     ISO Abbreviation:  J. Exp. Bot.     Publication Date:  2008  
Date Detail:
Created Date:  2008-05-26     Completed Date:  2008-10-30     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9882906     Medline TA:  J Exp Bot     Country:  England    
Other Details:
Languages:  eng     Pagination:  1695-703     Citation Subset:  IM    
Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, Canberra, Australian Capital Territory, 2601 Australia.
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MeSH Terms
Carbon Dioxide / metabolism*
Carbon Isotopes
Carbonic Anhydrases / metabolism
Malate Dehydrogenase / metabolism*
Photosynthesis / physiology*
Plant Leaves / enzymology
Poaceae / metabolism*
Reg. No./Substance:
0/Carbon Isotopes; 124-38-9/Carbon Dioxide; EC Dehydrogenase; EC dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); EC dehydrogenase (oxaloacetate-decarboxylating) (NADP+); EC Anhydrases

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