Pathways of nitrogen assimilation in cowpea nodules studied using /sup 15/N/sub 2/ and allopurinol. [Vigna unguiculata L. Walp. cv Vita]

Journal Article · Fri Jan 01 00:00:00 EST 1988 · Plant Physiol.; (United States)

OSTI ID:6905633

Atkins, C A; Storer, P J; Pate, J S

In the presence of 0.5 millimolar allopurinol (4-hydroxypyrazolo (3,4-d)pyrimidine), an inhibitor of NAD:xanthine oxidoreductase (EC 1.2.3.2), intact attached nodules of cowpea (vigna unguiculata L. Walp. cv Vita 3) formed (/sup 15/N)xanthine from /sup 15/N/sub 2/ at rates equivalent to those of ureide synthesis, confirming the direct assimilation of fixed nitrogen into purines. Xanthine accumulated in nodules and was exported in increasing amounts in xylem of allopurinol-treated plants. Other intermediates of purine oxidation, de novo purine synthesis, and ammonia assimilation did not increase and, over the time course of experiments (4 hours), allopurinol had no effect on nitrogenase (EC 1.87.99.2) activity. Negligible /sup 15/N -labeling of asparagine from /sup 15/N/sub 2/ was observed, suggesting that the significant pool (up to 14 micromoles per gram of nodule fresh weight) of this amide in cowpea nodules was not formed directly from fixation but may have accumulated as a consequence of phloem delivery.

• Research Organization: Univ. of Western Australia, Nedlands
• OSTI ID: 6905633
• Journal Information: Plant Physiol.; (United States), Vol. 86:1
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
NITROGEN
BIOLOGICAL PATHWAYS
XANTHINES
BIOLOGICAL ACCUMULATION
AMMONIA
ASPARAGINE
BIOSYNTHESIS
INHIBITION
LABELLED COMPOUNDS
NITROGEN 15
NITROGENASE
OXIDOREDUCTASES
PEAS
PURINES
TRACER TECHNIQUES
AMIDES
AMINO ACIDS
AROMATICS
AZAARENES
CARBOXYLIC ACIDS
ELEMENTS
ENZYMES
FOOD
HETEROCYCLIC COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NITRO-GROUP DEHYDROGENASES
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN ISOTOPES
NONMETALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PLANTS
STABLE ISOTOPES
SYNTHESIS
VEGETABLES
550201* - Biochemistry- Tracer Techniques