Dark CO/sub 2/ fixation and amino acid metabolism in symbiotic N/sub 2/-fixing systems. Labeling studies with /sup 14/C and /sup 13/N-labeled tracers. [Roots of soybean plants and alders]
Amino acid metabolism was examined by monitoring the amino acids labeled with (/sup 14/C) incorporated during dark CO/sub 2/ fixation and with (/sup 13/N) incorporated from /sup 13/NH/sub 4/+, /sup 13/NO/sub 3/- or (/sup 13/N)N/sub 2/. Label from /sup 14/CO/sub 2/ was directly incorporated in soybean roots and the N/sub 2/-fixing root nodules of soybeans and alders. The products of dark CO/sub 2/ fixation were primarily amino and organic acids. The distribution of label incorporated from /sup 14/CO/sub 2/ into amino acids depended on the plant species and the nitrigen source. The major labeled amino acids in roots and nodules of soybean plants dependent on N/sub 2/ were aspartate and glutamate; in alder nodules, citrulline; in roots of soybean plants treated with NO/sub 3/-, asparagine; and in roots of soybean plants treated with NH/sub 4/+, asparagine and glutamine. Asparagine was the major amino acid transported out of the soybean root system. Experiments indicated that asparagine was synthesized directly from aspartate. After exposure to /sup 14/CO/sub 2/, the specific activity of glutamine was consistently higher than that of glutamate in soybean nodules and roots of plants treated with NO/sub 3/-. This was taken as evidence that there were two pools of glutamate, only one of which was associated with glutamine synthesis. Alder and soybean nodules and roots were incubated with /sup 13/N-labeled tracers. Those tissues incubated with /sup 13/NH/sub 4/+ had a higher ratio of (/sup 13/N)glutamine to (/sup 13/N)glutamate that similar tissues exposed to /sup 13/NO/sub 3/- or (/sup 13/N)N/sub 2/. An explanation for these results based on the relative rates of glutamine and glutamate synthesis is discussed.
- OSTI ID:
- 6491087
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
553001* -- Agriculture & Food Technology-- Tracer Techniques-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
AMIDES
AMINO ACIDS
AMMONIUM COMPOUNDS
ASPARAGINE
BETA DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBON 14 COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
CITRULLINE
ELECTRON CAPTURE RADIOISOTOPES
GLUTAMINE
GLYCINE HISPIDA
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LEGUMINOSAE
LIGHT NUCLEI
METABOLISM
MINUTES LIVING RADIOISOTOPES
NITRATES
NITROGEN 13
NITROGEN COMPOUNDS
NITROGEN FIXATION
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLANTS
RADIOISOTOPES
ROOTS
TRACER TECHNIQUES
TRANSLOCATION
TREES