Nitrogenase activity in Trifolium subterraneum L. in relation to the uptake of nitrate ions. [Rhizobium trifolii]

Journal Article · Wed Jul 01 00:00:00 EDT 1987 · Plant Physiol.; (United States)

OSTI ID:5905041

Silsbury, J H

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), Vol. 84:3
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CLOVER
NUTRITION
NITROGENASE
ENZYME ACTIVITY
ACETYLENE
BIOLOGICAL ACCUMULATION
LABELLED COMPOUNDS
NITRATES
NITROGEN 15
NITROGEN FIXATION
NITROREDUCTASES
PLANT GROWTH
REDUCTION
RHIZOBIUM
TRACER TECHNIQUES
ALKYNES
BACTERIA
CHEMICAL REACTIONS
ENZYMES
GROWTH
HYDROCARBONS
ISOTOPE APPLICATIONS
ISOTOPES
LEGUMINOSAE
LIGHT NUCLEI
MICROORGANISMS
NITRO-GROUP DEHYDROGENASES
NITROGEN COMPOUNDS
NITROGEN ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PLANTS
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques