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Showing papers on "Nitrogen fixation published in 1972"


Journal ArticleDOI
TL;DR: The hydrogenase found in Rhizobium bacteroids is compared with that found in Azotobacter and found, in all respects examined, to be similar.
Abstract: The hydrogenase found in Rhizobium bacteroids is compared with that found in Azotobacter and found, in all respects examined, to be similar. When three host species were inoculated with Rhizobium, strain 311, different amounts of hydrogenase activity were found in Pisum sativum and Vicia bengalensis while the enzyme was absent from nodules of Vicia faba. Of four different strains of Rhizobium examined only two strains possessed the hydrogenase when present in pea root nodules. The role of the hydrogenase in nitrogen fixation is discussed and it is tentatively concluded that the overall efficiency of the nitrogen fixation process is increased by its presence.

276 citations


Journal ArticleDOI
TL;DR: High rates of acetylene reduction were observed in systems containing excised rhizomes of the Caribbean marine angiosperms Thalassia testudinum, Syringodium filiforme and Diplanthera wrightii, and the temperate marineAngiosperm Zostera marina.
Abstract: High rates of acetylene reduction were observed in systems containing excised rhizomes of the Caribbean marine angiosperms Thalassia testudinum, Syringodium filiforme and Diplanthera wrightii, and the temperate marine angiosperm Zostera marina. For 4 plant and plant-sediment systems the ratio of acetylene reduced/N2 fixed varied from 2.6 to 4.6. For T. testudinum the estimated rates of nitrogen fixation are in agreement with estimated requirements of the plant for nitrogen. For a typical T. testudinum stand, N2 fixation is estimated to be 100 to 500 kg N/hectare per year. Numbers of N2-fixing bacteria in the rhizosphere sediments were roughly 50 to 300 times more abundant than those in the nonrhizosphere sediments, and in both types of sediments were of the same orders as the estimated numbers of heterotrophic aerobes.

194 citations


Journal ArticleDOI
TL;DR: Yield-nutrient supply correlations indicate that a singnificant proportion of the phosphorus, and virtually all nitrogen for leaf growth are taken-up from the sediments, and that growth is generally limited by availability of nitrogen.
Abstract: How are high rates of production by Thalassia testudinum Konig maintained in notably nutrient-poor tropical waters? Yield-nutrient supply correlations indicate that a singnificant proportion of the phosphorus, and virtually all nitrogen for leaf growth are taken-up from the sediments, and that growth is generally limited by availability of nitrogen. Considerations of supply and demand suggest that the sediments could not be a primary source of phosphate, but the sediments may act as a “storage bank” for phosphate taken up from the sea water by T. testudinum. It is believed that inorganic nitrogen in the root layer is derived from fixation of gaseous nitrogen by anaerobic bacteria. Maintenance of anaerobic conditions in the root layer appears to be essential for good growth of T. testudinum, and it is suggested that such conditions facilitate nitrogen fixation.

178 citations


Journal ArticleDOI
TL;DR: A stepwise multiple regression analysis showed that fluctuations in N2 fixation were best described by variations in heterocysts, quantities of blue-green algae, PO4-P, NO3-N, and temperature.
Abstract: The annual contribution of N2 fixation to Clear Lake in 1970 was about 550 tonnes, 500 Mg (megagrams) or 18 kg ha−1, 43% of the lake’s yearly nitrogen inflow. Biological N2 fixation can provide the nitrogen for almost half the blue-green algal standing crop during blooms and is implicated as the main cause of large algal nuisance blooms on this lake. The large quantity of nitrogen fixed may be typical for large, shallow, cyanophyceandominated lakes. A sustained spring peak of fixation was associated with a simultaneous bloom of Aphanizomenon flos-aquae in all three basins, an autumn peak with an ephemeral bloom of Anabaena circinalis occurring at a different time in each basin. A stepwise multiple regression analysis showed that fluctuations in N2 fixation were best described by variations in heterocysts, quantities of blue-green algae, PO4-P, NO3-N, and temperature. Annual rates of N2 fixation were correlated with the proportion of heteroeysts to vegetative cells in Aphanizomenon and with total number of heterocysts in Anabaena. Previous nitrogen budgets for Clear Lake have shown a large excess of nitrogen in outflow over inflow, which is accounted for by the levels of N2 fixation measured.

153 citations


Journal ArticleDOI
27 Oct 1972-Nature
TL;DR: Genetic analysis of nitrogen fixation in free-living bacteria is being used to elucidate processes which in the plant root depend on a complex symbiotic relationship to increase the world resources of protein.
Abstract: Genetic analysis of nitrogen fixation in free-living bacteria is being used to elucidate processes which in the plant root depend on a complex symbiotic relationship. Increased understanding of the nitrogen fixation mechanism will eventually help to increase the world resources of protein.

85 citations



Book ChapterDOI
01 Jan 1972

69 citations


Journal ArticleDOI
TL;DR: Examination of root systems and adhering soil associated with unusually green corn plants from nitrogen-deficient areas in fields has revealed higher acetylene-reducing activities than comparable root systems of chlorotic plants that appeared to be nitrogen deficient.
Abstract: Examination of root systems and adhering soil associated with unusually green corn plants from nitrogen-deficient areas in fields has revealed higher acetylene-reducing activities than comparable root systems of chlorotic plants that appeared to be nitrogen deficient. From the root systems with acetylene-reducing activity, N2-fixing Enterobacter cloacae were isolated. Pure cultures of the organism grown in a medium lacking added fixed nitrogen reduced acetylene to ethylene and used N2 as a sole source of nitrogen under anaerobic conditions. Acetylene reduction was strikingly inhibited by 0.04 atm or greater partial pressures of O2; however, the bacteria maintained appreciable acetylene-reducing rates in medium exposed to partial pressures of O2 ranging from 0.005 to 0.015 atm. Nitrogenase activity in cell-free extracts of the bacterium was dependent upon Na2S2O4 and an ATP-generating system. Some environmental conditions expected to influence N2 fixation by free-living N2-fixing bacteria on root surfaces of nonlegumes are discussed.

66 citations


Journal ArticleDOI
TL;DR: The acetylene reduction assay was used to determine nitrogenase activity in a waterlogged soil–straw system and found that Nitrogenase activity was related to the number of nitrogen-fixing Clostridia.
Abstract: The acetylene reduction assay was used to determine nitrogenase activity in a waterlogged soil–straw system. Nitrogenase activity was related to the number of nitrogen-fixing Clostridia. The patter...

62 citations


Journal ArticleDOI
15 Dec 1972-Science
TL;DR: Nitrogen fixation by Dichothrix fucicola, an epiphyte on pelagic Sargassum, was measured in May and June 1972 in the western Sargasso Sea and the Gulf Stream, marking the first report of nitrogen fixation by a heterocyst-bearing blue-green alga in the open ocean.
Abstract: Nitrogen fixation by Dichothrix fucicola, an epiphyte on pelagic Sargassum, was measured in May and June 1972 in the western Sargasso Sea and the Gulf Stream. This is the first report of nitrogen fixation by a heterocyst-bearing blue-green alga in the open ocean, and also the first observation of nitrogen fixation in the genus Dichothrix. Cellular carbon/nitrogen ratios suggested that the Dichothrix was nitrogen-starved. In dense aggregations of Sargassum, such as rafts or windrows, the enrichment of surface seawater with combined nitrogen from nitrogen fixation may be pronounced.

54 citations


Journal ArticleDOI
TL;DR: The results suggest that the direct role of photosynthesis in nitrogen fixation is restricted to supply the energy by cyclic photophosphorylation at least under some experimental conditions.
Abstract: Experiments on the relationship between nitrogen fixation and photosynthesis in intact Anabaena cylindrica are reported.

Book ChapterDOI
TL;DR: Understanding of the biochemical relationships in symbiotic nitrogen fixation might allow the extension of this process to non-leguminous agricultural crops, and this chapter gives a general review of the field of nitrogen fixation with emphasis on recent developments.
Abstract: Publisher Summary Biological nitrogen fixation is the enzymic reduction of atmospheric nitrogen to ammonia. Along with the scientific interest of nitrogen fixation as a fundamental biochemical reaction, it is also of great ecological and agricultural importance because it is the most important source of the metabolizable nitrogen needed by all living organisms. Nitrogen fixation is catalyzed by nitrogenase, which requires energy in the form of ATP and a biologically strong reductant for the formation of ammonia. Moreover, the chapter also gives a general review of the field of nitrogen fixation with emphasis on recent developments. The study of the biochemical genetics of nitrogen fixation can yield important basic knowledge regarding the pathway, mechanism, and regulation of this process. Furthermore, in symbiotic nitrogen fixation, both plant and host bacterium carry genetic information relevant to this process, making the genetics of the system complex. Finally, understanding of the biochemical relationships in symbiotic nitrogen fixation might allow the extension of this process to non-leguminous agricultural crops.

Journal Article
TL;DR: In this article, a great deal of activity has been reported which, although it has not solved the problem, has given some indication of the systems and pathways involved in the reduction of nitrogen to ammonia.
Abstract: During the past ten years there has been a great deal of activity which, although it has not solved the problem, has given some indication of the systems and pathways involved in the reduction of nitrogen to ammonia.

Journal ArticleDOI
TL;DR: Several facultative asymbiotic N2-fixing bacteria exhibited nitrogenase activity when grown in the presence of air and a limiting amount of fixed nitrogen.
Abstract: Several facultative asymbiotic N2-fixing bacteria exhibited nitrogenase activity when grown in the presence of air and a limiting amount of fixed nitrogen. One isolate (S-4) identified as Klebsiell...

Book
01 Jan 1972
TL;DR: During the past ten years there has been a great deal of activity which has not solved the problem, but has given some indication of the systems and pathways involved in the reduction of nitrogen to ammonia.
Abstract: During the past ten years there has been a great deal of activity which, although it has not solved the problem, has given some indication of the systems and pathways involved in the reduction of nitrogen to ammonia.

Journal ArticleDOI
TL;DR: Effective white clover and soybean nodules contained more catalase than ineffective nodules, and a Rhizobium japonicum strain strain collected from effective soybeans nodules had great activity.
Abstract: Effective white clover and soybean nodules contained more catalase than ineffective nodules. The catalase activity of a Rhizobium japonicum strain collected from effective soybean nodules was great...

Journal ArticleDOI
TL;DR: Bacteria of the type identified on root surfaces of legumes were found often as contaminants of legume seeds and in most cases were not removed by surface sterilization treatments.
Abstract: Facultative anaerobic asymbiotic N2-fixing bacteria have been identified consistently on the surfaces of roots and nodules of soybean plants cultured under laboratory and greenhouse conditions. An ...

Journal ArticleDOI
TL;DR: In this article, the effects of Zn and P on growth, nodulation, and N fixation in two soybean varieties grown in solution cultures were investigated, and the results showed that Zinc deficiency decreased shoot weights, Zn concentrations in all plant parts, nodule weights, nodules leghemoglobin concentrations, and amounts of N fixed.
Abstract: Symbiotic N fixation by soybeans [Glycine max (L.) Merr.] is one factor determining yields of this important crop. Microelements have been shown to be important in metabolic processes in plants. This investigation was conducted to determine the effects of Zn and P on growth, nodulation, and N fixation, in two soybean varieties grown in solution cultures. Zinc deficiency decreased shoot weights, Zn concentrations in all plant parts, nodule weights, nodule leghemoglobin concentrations, and amounts of N fixed. Growth and P and Zn concentrations in one or more plant parts and nodule weights were greater for the P-tolerant variety than for the P-sensitive variety. Excess P decreased growth of all plant parts, nodule weights, nodule leghemoglobin concentrations, and amounts of N fixed. Nodule weights and amounts of N fixed were greater for the P-tolerant variety, particularly at the higher P level. Zinc deficiency and excess P may influence N fixation directly by affecting nodule nutrition and indirectly by affecting host nutrition.

Journal ArticleDOI
16 Aug 1972-Nature
TL;DR: High nitrogenase activity was demonstrated in heterocysts incubated aerobically and in cell-free preparations of Anabaena cylindrica and the non-heterocystous alga Plectonema boryanum strain 594, which tends to favour the suggestion that these cells are the sites of nitrogen enzyme activity.
Abstract: MANY blue-green algae fix nitrogen, assimilate carbon dioxide and evolve oxygen, and as algal nitrogenase is inhibited1–3 by high oxygen pressure, enhanced nitrogen fixation accompanying photosynthesis is surprising. Heterocysts do not contain4 or have comparatively less amounts4–7 of photosystem II (PS II) pigments, which are responsible for the evolution of oxygen. This tends to favour the suggestion of Fay et al.8 that these cells are the sites of nitrogenase activity. Until now, however, attempts at obtaining unequivocal evidence for heterocysts as principal loci for nitrogenase activity have yielded conflicting results. Stewart et al.7 first demonstrated nitrogenase activity in heterocysts incubated aerobically, a finding confirmed by Wolk and Wojciuch9 and Van Gorkom and Donze10. By contrast, Smith and Evans3,11 and Kurz and La Rue12 reported results favouring vegetative cells as the major site of nitrogenase activity. Other evidence2,13 showed high nitrogenase activity in cell-free preparations of Anabaena cylindrica and the non-heterocystous alga Plectonema boryanum strain 594.

Journal ArticleDOI
01 Jan 1972-Oikos
TL;DR: A method to determine the potential of microbial nitrogen fixation in soils under aerobic conditions is described and four different soil types were studied; loess, lime, mull and calcareous soil.
Abstract: A method to determine the potential of microbial nitrogen fixation in soils under aerobic conditions is described. Four different soil types were studied; loess, lime, mull and calcareous soil. The soil samples were collected in three different areas in Europe.

Journal ArticleDOI
TL;DR: The effects of two sources of nitrogen and ground corn cobs, applied either alone or in combination, on nitrogen fixation and seed yield of Glycine max (L.) Merr. cult Altona were investigated in an area where control plants fixed only 7.5 kg N2/ha as discussed by the authors.
Abstract: The effects of two sources of nitrogen and ground corn cobs, applied either alone or in combination, on nitrogen fixation and seed yield of Glycine max (L.) Merr. cult Altona were investigated in an area where control plants fixed only 7.5 kg N2/ha. Treatments were: N, 280 kg N/ha as NH4NO3; organic matter (O.M.), 14 T (dry wt)/ha of ground corn cobs as an organic matter source; N + O.M.; M1; 88 T/ha of liquid cattle manure; M1 + O.M.; M2, 176 T/ha of liquid cattle manure; M2 + O.M.; and C, control. Treatment effects on nitrogen fixation, measured as acetylene reduction rates, and seed yield were related to the levels of available N supplied to the plants. Nitrogen fixation was progressively increased by treatments M1, M2 + O.M., M1 + O.M., and O.M., with the latter two fixing seven times as much nitrogen as the control. Final seed yield, however, was increased by treatments supplying the highest levels of inorganic nitrogen to plants, with N and N + O.M. producing higher yields than the control plots.


Journal ArticleDOI
TL;DR: In this paper, short-term incubation studies of non-symbiotic nitrogen fixation using acetylene as the substrate for nitrogenase were carried out on six soil samples collected from various locations in the Western State of Nigeria, and on one soil sample collected from Wisconsin, U.S.A.
Abstract: Short-term incubation studies of non-symbiotic nitrogen fixation using acetylene as the substrate for nitrogenase were carried out on six soil samples collected from various locations in the Western State of Nigeria, and on one soil sample collected from Wisconsin, U.S.A. Unamended soils reduced a very small amount of acetylene but with added organic materials (5% organic matter, 2% glucose or sucrose) acetylene reduction became substantial and in one case was more than 30,000 times that in the unamended soil. In general, more acetylene was reduced in anaerobic than in aerobic soils. Two of the soils were tested for suppression of acetylene reduction by NH4+-N. With the addition of up to 100 ppm nitrogen as (NH4)2SO4 to the soils incubated with sucrose, no depression of acetylene reduction was observed in one soil while it was reduced by about half in the other.


Patent
10 Mar 1972
TL;DR: In this article, Nitrogen deficient waste is biooxidized from about 3 to about 12 hours in an aerated zone containing an active pure or semipure culture of aerobic free living nitrogen fixing bacteria.
Abstract: Nitrogen deficient waste is biooxidized from about 3 to about 12 hours in an aerated zone containing an active pure or semipure culture of aerobic free living nitrogen fixing bacteria.

Journal ArticleDOI
TL;DR: The relatively slow initial nodule development in Glycine is probably one of the important factors hindering the field establishment of seedlings, but in subsequent growth the symbiosis appears fully effective.
Abstract: The growth, nodulation, and nitrogen fixation of Glycine wightii cv. Cooper (Glycine) and Phaseolus atropurpureus cv. Siratro (Siratro) were compared in a glasshouse, sand culture techniques being used in a series of trials encompassing a full range of seasonal environments. Plants were inoculated with the commercial Rhizobium strain (CB756) for both species either at germination or 12 days later when seed reserves were virtually exhausted. In both early and late inoculation treatments, Siratro nodulated and established nitrogen fixation more rapidly than did Glycine. This difference between the species was not directly associated with the marked difference in seed size. When active nitrogen fixation was fully established, the disadvantage shown by Glycine in the early nodulation phase was not evident, and the treatments were similar in the rate of growth and nitrogen accumulation, proportion of nodule weight to whole plant weight, proportion of pigmented nodules, efficiency of nitrogen fixation, and concentration of nitrogen in the whole plant. The relatively slow initial nodule development in Glycine is probably one of the important factors hindering the field establishment of seedlings, but in subsequent growth the symbiosis appears fully effective.


Journal ArticleDOI
TL;DR: The effect of the exudates of Azotobacter chroococcum in nitrogen-free liquid medium and in sterile soil, on its ability to fix nitrogen was studied as discussed by the authors.
Abstract: The effect of the exudates of Azotobacter chroococcum in nitrogen-free liquid medium and in sterile soil, on its ability to fix nitrogen was studied. Cell-free culture filtrates and water extract of sterile soil inoculated with Azotobacter were fractionated into ether soluble and insoluble aliquots, concentrated and chromatographically separated into ten consecutive zones. These were eluted and tested for their effect on nitrogen fixation by Azotobacter. UV-fluorescence, and chemical tests for indoles, reducing substances, amino acids, and hydroxyl groups were made. Detection of gibberellins and water soluble vitamins was attempted. A biological test for activity of indolic compounds was carried out. The results showed that Azotobacter produces biologically active indolic compounds in culture and soil, acting as a significant stimulation for the process of nitrogen fixation. Not all the zones of the chromatogram which were stimulatory for nitrogen fixation were the same for coleoptile growth and vice versa. Amino acids in some cases were associated with non-significant stimulation of nitrogen fixation. An indication was obtained suggesting the possible stimulation of nitrogen fixation by gibberellins produced in culture and soil by Azotobacter. Suggestion was given for studying the effect of individual gib berellic compounds on the nitrogen fixation process, with a view to their interaction with amino acids and indolic compounds.

Journal ArticleDOI
01 Jan 1972-Oikos
TL;DR: In this article, the main contribution to the system as a whole is made by Lotus corniculatus and the limitations of this pilot study are discussed together with the potential of the acetylene reduction assay in ecological investigations.
Abstract: Soil cores and detached nodules of four plant species were assayed for nitrogen fixation by the acetylene reduction method. The vegetation of the dunes was analysed and an attempt made to estimate the relative contribution of fixed nitrogen by different species by relating the two sets of results. It is concluded that the main contribution to the system as a whole is made by Lotus corniculatus. The limitations of this pilot study are discussed together with the potential of the acetylene reduction assay in ecological investigations.

Journal ArticleDOI
TL;DR: In this article, the authors examined biological nitrogen fixation, inorganic complexes related to N2ase, and non-enzymatic nitrogen fixation in terms of inorganic nitrogen fixation.
Abstract: Examines biological nitrogen fixation, inorganic complexes related to N2ase, and non-enzymatic nitrogen fixation