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  • Nitrogen fixation
  • Springer  (4)
  • Periodicals Archive Online (PAO)
  • 1975-1979  (4)
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  • Springer  (4)
  • Periodicals Archive Online (PAO)
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  • 1
    ISSN: 1432-2048
    Keywords: Leguminosae ; Nitrate-reductase mutants ; Nitrogen fixation ; Nodulation ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g−1 nodule fr. wt. h−1), were both affected by the added nitrate.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 107 (1976), S. 115-124 
    ISSN: 1432-072X
    Keywords: Alanine dehydrogenase ; Anabaena cylindrica ; Heterocysts ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The l-alanine dehydrogenase (ADH) of Anabaena cylindrica has been purified 700-fold. It has a molecular weight of approximately 270000, has 6 sub-units, each of molecular weight approximately 43000, and shows activity both in the aminating and deaminating directions. The enzyme is NADH/NAD+ specific and oxaloacetate can partially substitute for pyruvate. The K m app for NAD+ is 14 μM and 60 μM at low and high NAD+ concentrations, respectively. The K m app for l-alanine is 0.4 mM, that for pyruvate is 0.11 mM, and that for oxaloacetate is 3.0 mM. The K m app for NH 4 + varies from 8–133 mM depending on the pH, being lowest at high pH levels (pH 8.7 or above). Alanine, serine and glycine inhibit ADH activity in the aminating direction. The enzyme is active both in heterocysts and vegetative cells and activity is higher in nitrogen-starved cultures than in N2-fixing cultures. The data suggest that although alanine is formed by the aminating activity of ADH, entry of newly fixed ammonia into organic combination does not occur primarily via ADH in N2-fixing cultures of A. cylindrica. Ammonia assimilation via ADH may be important in cultures with an excess of available nitrogen. The deaminating activity of the enzyme may be important under conditions of nitrogen-deficiency.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 53 (1979), S. 319-328 
    ISSN: 1573-5036
    Keywords: Dolichos ; Growth ; Greenhouse ; Lablab ; Leaf area ; Nitrogen fixation ; Nodulation ; Sand culture ; Sugars ; Sulfur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In order to explore interrelations between S nutrition, soluble sugars, leaf area, nodulation and N2 fixation, greenhouse experiments were done with several levels of S added to perlite-sand cultures or to a moderately S-deficient soil. Sulfur had indirect effects on nodulation and N2 fixation, possibly by improving sugars supply and N metabolism. In perlite-sand culture, leaf area increased with concentrations of supplied S up to 50 and 200 μM for symbiotic and N-treated plants respectively, then decreased at higher concentrations. Plant yield and total sugars content (mg per plant) for the N-treated plants behaved similar to leaf area in response to added S but in the symbiotic plants maximum values were obtained at 100 μM S. In soil, Mo had no effect on growth but interacted significantly with S in affecting total sugars content. High levels of S depressed sugars content at low Mo but raised it at high Mo. Sulfur increased the N content of soil-grown plants. It increased the N content of plants grown in perlite-sand culture except at very high levels of S. There was little effect on concentration of N in the shoots. Nitrogen content correlated significantly with leaf area and sugar content, and highly significantly with S concentration in the shoots.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 52 (1979), S. 571-578 
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Actinomycetous symbiosis ; Alnus glutinosa ; Hydrogenase Hydrogen evolution ; Hydrogen uptake ; Nitrogen fixation ; Respiration ; Root nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In the growing season no net H2 evolution is detected when root nodules ofAlnus glutinosa are incubated in air or in argon containing 20% O2. Due to the hydrogenase activity, N2-fixing root nodules consume added H2 at a rate of about 1.4 μmoles H2.g fresh nodule−1.h−1. The uptake of H2 is only found in summer. At the end of the season, in autumn, nodules evolve significant quantities of H2 although the nodules still continue to fix nitrogen. In-vitro studies with fractionated homogenates of summer-harvested nodules show that the recovery of the hydrogenase is high when using methylene-blue or phenazine metasulfate as electron acceptors. No hydrogenase activity is detected in homogenates of autumn-harvested nodules. The hydrogenase is localised in the microsymbiont.
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