Nitrogenase activity in Trifolium subterraneum L. in relation to the uptake of nitrate ions. [Rhizobium trifolii]
An experiment was conducted to test the hypothesis that, when nitrogenase and nitrate reductase both contribute to the nitrogen nutrition of a nodulated legume, nitrogenase activity is inversely proportional to the rate of accumulation of organic nitrogen derived from the reduction of nitrate. Trifolium subterraneum L. plants, inoculated with Rhizobium trifolii and sown as small swards, were allowed to establish a closed canopy and steady rates of growth, dinitrogen fixation, and nitrogen accumulation. Swards were then supplied with nutrient solutions of 0, 0.5, 1.0, or 2.5 mM NO/sub 3//sup -/ with a 29.69% enrichment of /sup 15/N and allowed to grow for a further 33 days. Harvests were made to measure dry weight, nitrogen accumulation, /sup 15/N accumulation, NO/sub 3//sup -/ content and nitrogenase activity by acetylene reduction assay. Since the /sup 15/N of the plant organic matter could have been derived only from the NO/sub 3//sup -/ of the nutrient solution, its rate of accumulation provided a measure of the rate of NO/sub 3//sup -/ reduction. It was found that as this rate increased in response to external NO/sub 3//sup -/ concentration the rate of nitrogenase activity decreased proportionately. It is concluded that the reduction of nitrate and the reduction of dinitrogen act in a complementary manner to supply a plant with organic nitrogen for growth.
- Research Organization:
- Univ. of Adelaide, Glen Osmond, Australia
- OSTI ID:
- 5905041
- Journal Information:
- Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 84:3; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
Similar Records
Influences of soil acidity and variety of plant on the populations of Rhizobium trifolii found in nodules of Trifolium subterraneum L
Genome sequence of the clover-nodulating Rhizobium leguminosarum bv. trifolii strain SRDI943.
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ACETYLENE
ALKYNES
BACTERIA
BIOLOGICAL ACCUMULATION
CHEMICAL REACTIONS
CLOVER
ENZYME ACTIVITY
ENZYMES
GROWTH
HYDROCARBONS
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
LEGUMINOSAE
LIGHT NUCLEI
MICROORGANISMS
NITRATES
NITRO-GROUP DEHYDROGENASES
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN FIXATION
NITROGEN ISOTOPES
NITROGENASE
NITROREDUCTASES
NUCLEI
NUTRITION
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PLANT GROWTH
PLANTS
REDUCTION
RHIZOBIUM
STABLE ISOTOPES
TRACER TECHNIQUES