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The role of dark carbon dioxide fixation in root nodules of soybean.
MedLine Citation:
PMID:  16664774     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
The magnitude and role of dark CO(2) fixation were examined in nodules of intact soybean plants (Harosoy 63 x Rhizobium japonicum strain USDA 16). The estimated rate of nodule dark CO(2) fixation, based on a 2 minute pulse-feed with (14)CO(2) under saturating conditions, was 102 micromoles per gram dry weight per hour. This was equivalent to 14% of net nodule respiration. Only 18% of this CO(2) fixation was estimated to be required for organic and amino acid synthesis for growth and export processes. The major portion (75-92%) of fixed label was released as CO(2) within 60 minutes. The labeling pattern during pulse-chase experiments was consistent with CO(2) fixation by phosphoenolpyruvate carboxylase. During the chase, the greatest loss of label occurred in organic acids. Exposure of nodulated roots to Ar:O(2) (80:20) did not affect dark CO(2) fixation, while exposure to O(2):CO(2) (95:5) resulted in 54% inhibition. From these results, it was concluded that at least 66% of dark CO(2) fixation in soybean may be involved with the production of organic acids, which when oxidized would be capable of providing at least 48% of the requirement for ATP equivalents to support nitrogenase activity.
Authors:
B J King; D B Layzell; D T Canvin
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  81     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1986 May 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-06-29     Revised Date:  2010-09-14    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  200-5     Citation Subset:  -    
Affiliation:
Department of Biology, Queen's University, Kingston, Ontario K7L 3N6 Canada.
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