Ontogenetic Interactions between Photosynthesis and Symbiotic Nitrogen Fixation in Legumes

Photosynthetic data collected from Pisum sativum L. and Phaseolus vulgaris L. plants at different stages of development were related to symbiotic N2 fixation in the root nodules. The net carbon exchange rate of each leaf varied directly with carboxylation efficiency and inversely with the CO2 compen...

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Bibliographic Details
Published in:Plant physiology (Bethesda) 1977-09, Vol.60 (3), p.419-421
Main Authors: Bethlenfalvay, Gabor J., Phillips, Donald A.
Format: Article
Language:English
Subjects:
Carbon dioxide
Carboxylation
Leaves
Nitrogen fixation
Peas
Photosynthesis
Planting
Plants
Root nodules
Symbiosis
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Summary:Photosynthetic data collected from Pisum sativum L. and Phaseolus vulgaris L. plants at different stages of development were related to symbiotic N2 fixation in the root nodules. The net carbon exchange rate of each leaf varied directly with carboxylation efficiency and inversely with the CO2 compensation point. Net carbon exchange of the lowest leaves reputed to supply fixed carbon to root nodules declined in parallel with H2 evolution from root nodules. The decrease in H2 evolution also coincided with the onset of flowering but preceded the peak in N2 fixation activity measured by acetylene-dependent ethylene production. A result of these changes was that the relative efficiency of N2 fixation in peas increased to 0.7 from an initial value of 0.4. The data reveal that attempts to identify photosynthetic contributions of leaves to root nodules will require careful timing and suggest that the relative efficiency of N2 fixation may be influenced by source-sink relationships.
ISSN:0032-0889
1532-2548
DOI:10.1104/pp.60.3.419