Showing papers on "Nitrogen fixation published in 1971"
TL;DR: It is now possible to devote an entire review to the biochemistry of symbiotic nitrogen fixation, although most of the information has come from the study of only four legu mes-soybeans, lupines, serradella.
Abstract: to be solved. For example, the role of each of the two components of the complex is not known and the high requirement for energy from ATP is not understood. Most recent reviews, including those from authors other than the above (37, 62, 66, 106), have included references to symbiotic systems. It is now possible to devote an entire review to the biochemistry of symbiotic nitrogen fixation, although most of the information has come from the study of only four legu mes-soybeans, lupines, serradella,
156 citations
01 Jan 1971
103 citations
101 citations
TL;DR: Electron micrographic analysis of the developmental morphology of the natural soybean symbiosis and C2H2-C2H4 analysis indicate that increasing N2-fixing activity from 12–35 days of age is accompanied by an increase in bacteroid number per cell, bacteroids number per vesicle and inclusions per bacteroid, which is consistent with a proposed mechanism.
Abstract: 1. Characteristics and methodology of the C2H2-C2H4 assay forin situ measurement of N2 fixation are outlined. 2. Electron micrographic analysis of the developmental morphology of the natural soybean symbiosis and C2H2-C2H4 analysis indicate that increasing N2-fixing activity from 12–35 days of age is accompanied by an increase in bacteroid number per cell, bacteroid number per vesicle and inclusions per bacteroid. The mole ratio of leghemoglobin to nitrogenase also increases from 50 to a relatively constant plateau of 500 to 1500 during this period. The quantitative validity of the C2H2-C2H4 assay as a measure of N2 fixation during a complete growth cycle of soybeans on nitrogen-free medium is demonstrated by Σ (C2H2→C2H4)×28/3 values which are 75–95% of the values determined for N2 fixed by Kjeldahl analyses. 3. A technique for the establishment of the first callus N2-fixing symbiosis in mixed cultures ofRhizobium legume provides a defined experimental system for exploration of legume symbiosis. N2-fixing activity is about 1% of the natural system and is influenced by exogenous auxins and cytokinins. Morphology, including infection threads and vesicle enclosed bacteroids, is similar to the nodule system. 4. N2-fixing activity of field-grown soybeans, including varieties which differed in flowering characteristics and maturity dates, and of peanuts was determined biweekly with the C2H2-C2H4 assay. Activity extended from nodule initiation to senescence and correlated with the nitrogen demands of the plant and in most cases >90% of the N2 fixed during the 60–70 day period of fruit formation and maturation. A logarithmic relationship between N2-fixing activity and age, and N2 fixed and age was demonstrated as a fundamental characteristic of these annual symbionts,i.e. log N2 fixed =k(t−t
0), wheret
0 is age at activity initiation. The resultant parameters: 1) age at activity initiation, 2) calculated rate of daily increase (7–9% for soybeans and 7–10% for peanuts), 3) age at end of logarithmic phase (about 80 days for soybeans), and 4) total N2 fixed (about 250 mg per soybean plant) are useful bases for evaluation of environmental, bacterial and host effects on N2 fixation. Various N fertilizers applied at planting and flowering inhibited N2 fixation of soybeans by decreasing the rate of daily increase. 5. Physical and chemical characteristics of nitrogenase, including those of crystalline Mo-Fe protein, reactions of nitrogenase, and model studies are consistent with a proposed mechanism. 6. Potential utilities of N2 fixation research include increased food protein production via initially enhanced N2 fixation of legumes such as soybeans and eventually extension of N2-fixing symbioses to non-legumes and new chemistry of N2, including the direct incorporation of aerial N2 into important organic compounds.
99 citations
TL;DR: The study of biological nitrogen fixation at the genetic level has been restricted by the lack of a suitable method of gene transfer in nitrogen-fixing bacteria as mentioned in this paper, but the transfer and mapping of the nitrogen fixation genes have not so far been possible.
Abstract: THE study of biological nitrogen fixation at the genetic level has been restricted by the lack of a suitable method of gene transfer in nitrogen-fixing bacteria. Mutants of Azotobacter vinelandii1,2 and Clostridium pasteurianum3 defective in nitrogen fixation have been isolated and characterized, but the transfer and mapping of the nitrogen fixation (nif) genes have not so far been possible.
97 citations
TL;DR: In situ fixation of molecular nitrogen was mcasurcd in the pelagial of Lake Erkcn by the acetylene reduction technique every 2 weeks during a period of 5 months, and showed highest nitrogenase activity in the first period of algal development.
Abstract: In situ fixation of molecular nitrogen was mcasurcd in 19170 in the pelagial of Lake Erkcn by the acetylene reduction technique every 2 weeks during a period of 5 months. The diurnal cycles and vertical distribution of algae were also investigated. Fixation was correlated with the presence of heterocystous blue-green algae, especially Aphanixomenon, in the phytoplankton, and was light dependent, though appreciable dark fixation also occurred, owing to endogenous utilization of photosynthetic products formed during previous light periods. The annual contribution of nitrogen fixation in the pelagial was of the order 0.5 g N/m’. The highest values were obtained before mass development of Aphanixomenon and maximal primary production. The algae showed highest nitrogenase activity in the first period of algal development. Lake Erken is moderately eutrophic and unpolluted. The contribution of easily available combined nitrogen by pelagic nitrogen fixation increases the annual loading of combined nitrogen by 40% and must therefore be considered quite important.
90 citations
TL;DR: Estimates of numbers of these species indicate that they will be responsible for only very low rates of nitrogen fixation in the soils tested.
Abstract: SUMMARY: The screening of several hundred isolates from tussock-grassland soils for nitrogen-fixing ability resulted in the isolation of Clostridium butyricum and five facultatively anaerobic nitrogen-fixing species. These latter have been identified as Bacillus circulans (tentative identification), B. polymyxa, Enterobacter aerogenes (formerly Aerobacter aerogenes), Klebsiella pneumoniae and Escherichia intermedia.
Estimates of numbers of these species indicate that they will be responsible for only very low rates of nitrogen fixation in the soils tested.
76 citations
TL;DR: A pea cultivar, resistant to the majority of Rhizobium strains when growing at 20°C, is found to require a short period of a higher temperature for successful nodulation.
Abstract: An outline is given of the possibility selecting Rhizobium strains capable of performing a relatively good symbiosis with leguminous plants, growing under stress conditions. A Rhizobium strain capable of nodulating pea plants in acid soils is described. A pea cultivar, resistant to the majority of Rhizobium strains when growing at 20°C, is found to require a short period of a higher temperature for successful nodulation. The effect of non-photosynthetic light and its possible significance under natural conditions is discussed.
74 citations
TL;DR: In this paper, it was shown that carbon dioxide at a concentration of 3 ppm completely inhibits nodulation, while at concentrations of 0.4 ppm and above it is extremely inhibitory towards nodulation.
Abstract: At a concentration of 3%, carbon dioxide completely inhibits nodulation. Ethylene at concentrations of 0.4 ppm and above is extremely inhibitory towards nodulation. The gaseous emanations from isolated root cultures, when permitted to accumulate, completely prevent nodulation and also inhibit the nitrogen fixation of existing nodules. Evidence is presented which suggests that ethylene is the active principle of the gaseous emanations.
72 citations
TL;DR: Evidence is provided that non-heterocystous blue-green algae may fix nitrogen if grown under low oxygen tension, so that heterocysts are not essential for nitrogen fixation in these algae.
Abstract: THE function of heterocysts in blue-green algae has been controversial for some time; there are indications that these enlarged cells are the site of nitrogen fixation1,2. But non-heterocystous blue-green algae may fix nitrogen if grown under low oxygen tension3, so that heterocysts are not essential for nitrogen fixation in these algae. According to a current hypothesis4, in aerobic conditions nitrogen fixation is confined to heterocysts, while in anaerobic or semi-anaerobic conditions the vegetative cells fix nitrogen as well. We have evidence to support this view.
TL;DR: The results emphasize the importance of the bacterial nitrogen fixation in the rhizosphere which had been hitherto overlooked.
Abstract: The nitrogen fixing activity of three Ivory Coast soils was tested in the laboratory by the acetylene reduction assay and the Kjeldahl method. Nitrogen fixation due to algae was estimated to be of the order of 4 to 8 (acetylene method) and 7 μg N per g soil per day (Kjeldahl method). Nitrogen fixation due to bacterial activity in the rice rhizosphere was estimated to be of the order of 2 to 5 (acetylene method) and 1 to 3 μg N per g soil per day (Kjeldahl method). These results emphasize the importance of the bacterial nitrogen fixation in the rhizosphere which had been hitherto overlooked. Comparison of acetylene method and Kjeldahl method results shows discrepancies the origin of which has been discussed. Time course of acetylene reduction by rhizosphere soils exhibits a lag phase which may be attributed to Postgate's switch off — switch on process.
TL;DR: Several experimental conditions were relevant in maintaining consistently high activities of Rhodospirillum rubrum, and the amount of gas taken up by the cells agreed quantitatively with the increase of bound nitrogen found in the cells by microkjeldahl determinations.
Abstract: Whole cells of Rhodospirillum rubrum were cultivated in a malate medium lacking bound nitrogen under N2 and tested for their nitrogenase activity by measuring the disappearance of nitrogen manometrically.
TL;DR: It is suggested that water supply has a major effect on the amount of nitrogen fixed in the field, particularly in those legumes which have nodules near the soil surface.
Abstract: Water stress is known to affect the formation and longevity of leguminous root nodules. Work in Dundee has shown that it also affects rates of nitrogen fixation in nodules, lichens and blue-green algae.
TL;DR: It can be concluded that photosynthetic bacteria contribute very significantly to soil fertility and improvement of the plant growth condition.
Abstract: The nitrogen fixation ability ofRhodopseudomonas capsulatus (a member of the photosynthetic bacteria) has been investigated. This organism can fix N2 most effectively under illuminated anaerobic conditions. However, in mixed culture in symbiotic association with heterotrophic bacteria, this microorganism using pyruvic acid excreted by the heterotrophs is capable of fixing nitrogen even under an apparent aerobic environment.
01 Jan 1971
TL;DR: Experiments in which legumes and non-legumes were cultured in sterile soil with and without non-sterile extracts of garden soil provided conclusive evidence that the non-terile extract was needed for nodulation and that nodulation was essential for normal growth without adequate combined nitrogen.
Abstract: The beneficial effects of including legumes in crop rotations were realized by early Greek, Roman and Chinese agriculturists centuries before the elementary principles of biological N2 fixation were established (Fred, Baldwin and McCoy, 1932; Stewart, 1966). Although the occurrence of nodules on roots of legumes had been described (Malpighi, 1675), and evidence for N2 fixation by leguminous plants in field plots had been reported (Boussingault, 1838), the basic biological aspects of symbiotic N2 fixation by legumes were not established until the results of the classical experiments of Hellriegel and Wilfarth (1888) were reported. They assumed that nodules on the roots of Pisum sativum were caused by bacteria and that nodulation enabled the plants to fix N2. Furthermore, both non-legumes and leguminous plants without nodules were considered to be dependent upon fixed nitrogen compounds in the soil. Experiments in which legumes and non-legumes were cultured in sterile soil with and without non-sterile extracts of garden soil provided conclusive evidence that the non-sterile extract was needed for nodulation and that nodulation was essential for normal growth without adequate combined nitrogen.
TL;DR: In this paper, the effect of soil water suction and root temperature on rates of nitrogen fixation, transpiration, and net photosynthesis of soybeans (Glycine max (L.) Merr.) was studied in laboratory experiments.
Abstract: The effect of soil water suction and root temperature on rates of nitrogen fixation, transpiration, and net photosynthesis of soybeans (Glycine max (L.) Merr.) was studied in laboratory experiments. The range of root temperature and soil water suction considered was 15.6 to 37.8 C and 0.30 to 2.50 bars, respectively. With increasing root temperature rates of nitrogen fixation, transpiration and photosynthesis increased slowly at first and then rapidly until an optimum temperature was reached followed by a decrease at higher temperatures. Optimum temperatures were 27, 30, and 27 C for rates of nitrogen fixation, transpiration, and net photosynthesis, respectively. Rates of the three paralneters decreased with increasing soil water suction. The amount of nitrogen fixed per unit of CO₂ absorbed was highest at a root temperature of 23.9 C and lowest at 37.8 C. This ratio decreased with increasing soil water suction at all temperatures considered. Changes in transpiration rate resulting from changes in soil temeprature were attributed to temperature effects on viscosity and metabolic activity. Effects of soil water suction and soil temperature on nitrogen fixation indicated in this study emphasize the complex symbiotic nature of the process. Mechanisms by which the two environmental parameters might affect the rate of fixation were indicated but not clearly elucidated by the results of the experiments.
TL;DR: Azotobacter and nitrogen-fixing clostridia are ubiquitous soil inhabitants in Egypt, Iraq and probably in all of the Near East and they occur in high numbers except where barrenness, NaCl accumulation or other depressing factors exist.
Abstract: Azotobacter and nitrogen-fixing clostridia are ubiquitous soil inhabitants in Egypt, Iraq and probably in all of the Near East. They occur in high numbers except where barrenness, NaCl accumulation or other depressing factors exist. The soil environment has proved favourable for their development since their response to supplementation with energy materials is quite marked. The organisms are resistant to drought, but optimal activity of Azotobacter is around 60% W.H.C. while that of clostridia is at 100%. Azotobacter as well as clostridia show optimal activity around 30°C, higher temperatures favour clostridia while lower ones favour Azotobacter. Gains of soil nitrogen are linked to the growth of Azotobacter rather than to that of Clostridium. The amounts of nitrogen gained and fixation efficiency are affected by the nature of the substrate, being greatest in clay, then in sand and calcareous soils and least in liquid media. Phosphate is essential, favouring nitrogen fixation firstly by satisfying the high phosphate requirement of Azotobacter and secondly by increasing the rate of decomposition of otherwise unavailable material. Gains of combined nitrogen and fixation efficiency are also affected by the type of organic matter added. A wide C/N ratio and susceptibility to decomposition are specially beneficial properties. Plant residues enrich the soil with nitrogen, partly by enhancing nitrogen fixation and partly by causing immobilization of mineral nitrogen which would otherwise be leached out of the soil by irrigation.
TL;DR: In this article, Nitrogen fixation in the natural, Agropyron-Koeleria grassland ecosystem was studied using the C2H2-C2H4 and N15 assays.
Abstract: Nitrogen fixation in the natural, Agropyron-Koeleria grassland ecosystem was studied using the C2H2-C2H4 and N15 assays. Small soil samples and also undisturbed soil cores were used for analyses. Both techniques indicated that grassland and associated cultivated soils had low fixation rates (0.6–1.8 kg/ha per 28 days in the laboratory and, 1 kg/ha per season under actual field conditions). Algal colonies (Nostoc spp.) on the soil surface were active fixers when the surface of the grassland was moist. However, their small biomass limits the extent of fixation in most areas.
TL;DR: The extent of fixation by free-living algae in soil at three locations near Uppsala is discussed and compared with fixation by symbiotic algae living as phycobionts or cephalodia in lichens.
Abstract: A review of the few earlier investigations of nitrogen fixation by blue-green algae in temperate soils is presented. The extent of fixation by free-living algae in soil at three locations near Uppsala is discussed and compared with fixation by symbiotic algae living as phycobionts or cephalodia in lichens.
TL;DR: The most vigorous nitrogen-fixing blue-green algae have been assessed for use as green manure in rice fields and favorable effects have been reported in India and other countries.
Abstract: a)Nitrogen fixation in rice fields. Nitrogen-fixing blue-green algae grow abundantly in tropical regions and are particularly common in paddy fields. Their possible role in the nitrogen accumulation of soil has been studied. The most vigorous nitrogen-fixing blue-green algae have been assessed for use as green manure in rice fields and favorable effects have been reported in India and other countries.
TL;DR: In this article, the preparation and properties of dihydridodinitrogen complexes of iron(II), FeH2(N2)L3(L=PetPh2, PBuPh2) are described.
TL;DR: Ryegrass without nitrogen fertilizer was a better measure of the amounts of nitrogen obtainable from the soil because the introduced ineffective strains were overgrown by effective strains in the second year.
Abstract: Field experiments at five sites (two on clay loam, two on a sandy soil and one on chalky loam) compared dry-matter yields and nitrogen contents of lucerne and ryegrass. These tested Rhizobium inoculation and fertilizer treatments in an experimental design proposed by Vincent and Nutman (IBP 69(66), amended 57/68). The crop and inoculation treatments (using large inocula of effective or ineffective strains) were set out in strips across each site to minimise contamination, and the fertilizer treatments (nitrogen, limeetc.) distributed at random within strips. This proved satisfactory and allowed valid statistical analysis. The massive inoculation with the ineffective strain suppressed the few naturally occurring effectiveR. meliloti at some of the sites, and provided a basis of comparison for assessing the amounts of nitrogen fixed by the native strains and by the introduced effective strains. However, it did so only during the first year because the introduced ineffective strains were overgrown by effective strains in the second year. Hence, ryegrass without nitrogen fertilizer was a better measure of the amounts of nitrogen obtainable from the soil. Estimates of fixation ranged from 0 to more than 300 kg N ha−1 at the different sites, treatment comparisons indicating the main factors limiting fixation. Parallel experiments were done using a soil core technique described by Vincent. These gave very similar results to the field trials in their first years.
TL;DR: The response of Rhodes grass to nitrogen applied as sodium nitrate, ammonium sulphate, urea, or ammonium nitrate-limestone at rates of 56, 112, 224, and 448 kg N ha-1 year-1 was measured in small plots over seven years at the Samford Pasture Research Station.
Abstract: The response of Rhodes grass to nitrogen applied as sodium nitrate, ammonium sulphate, urea, or ammonium nitrate-limestone at rates of 56, 112, 224, and 448 kg N ha-1 year-1 was measured in small plots over seven years at the Samford Pasture Research Station. The ranking order of mean yields of dry matter and nitrogen at the fertilizer rates where Rhodes grass remained dominant (the 224 and 448 kg rates) was sodium nitrate> ammonium nitrate-limestone> urea. At these rates ammonium sulphate was about as effective as sodium nitrate, until the comparison was confounded by changes in soil pH. The comparative efficiency of urea varied widely between harvests. Taking the weighted mean for the 224 and 448 kg rates over seven years, urea gave 87 per cent of the nitrogen yield that sodium nitrate gave. On plots receiving 0 to 112 kg N, Rhodes grass was replaced progressively by other species, chiefly Digitaria spp., ,Axonopus affinis, and Glycine tabacina. Negative apparent nitrogen recoveries recorded from the 56 and 112 kg N treatments in the seventh year were attributed to a bias caused by nitrogen fixation by native legumes. Nitrogen fertilization caused a significant increase in the nitrogen content of soil and roots (0-15 cm) at the end of the experiment. The increase was significantly smaller with ammonium sulphate than with other forms. About 20-40 per cent of the fertilizer nitrogen added over seven years could not be accounted for in top growth or in soil plus roots. A microplot study with 15N-labelled ammonium- and nitrate-N in the seventh year showed an apparent loss of added 15N, which increased with fertilizer rate, of from 5 to 43 per cent.
TL;DR: Data on nitrogen fixation by cell-free extracts of blue-green algae is presented on the effects of oxygen and other physiological parameters on nitrogenase activity and on the ecological distribution of the group.
Abstract: The various types of blue-green algae known to fix nitrogen are considered. Particular attention has been paid to the effects of oxygen and other physiological parameters on nitrogenase activity and on the ecological distribution of the group. Data on nitrogen fixation by cell-free extracts of blue-green algae are presented.
TL;DR: Determinations in the open waters of lakes using N15 as a tracer show that nitrogen fixation is generally associated with the presence of heterocystous blue-green algae and is light dependent, and nitrogen fixation per unit area of lake surface per year tends to be greatest at an early stage of eutrophication.
Abstract: Determinations in the open waters of lakes using N15 as a tracer show that nitrogen fixation is generally associated with the presence of heterocystous blue-green algae and is light dependent. Although nitrogen-fixing blue-green algae tend to be abundant when the concentration of nitrate or ammonia in the water is low, fixation itself is not necessarily inhibited by the presence of these sources of combined nitrogen. The activity of nitrogen-fixing blue-green algae shows a direct relationship to concentration of dissolved organic nitrogen.
TL;DR: In this paper, inoculation with rhizobium japonicum inoculation increased soybean yields and the additional fixed nitrogen removed by soybeans amounted to 40 to 120 kg ha−1.
Abstract: Phosphate increased nitrogen uptake by lucerne appreciably on a saline soil. Nitrogenous fertiliser or inoculation with an effective strain ofRhizobium meliloti did not increase the yield significantly. In soils where indigenousRhizobium japonicum was absent inoculation increased soybean yields and the additional fixed nitrogen removed by soybeans amounted to 40 to 120 kg ha−1. Gram and groundnut also responded to Rhizobium inoculation in field trials.
TL;DR: Results indicate that a cytokinin-like substance is involved in leaf-nodulated Psychotria mucronata seedlings grown in N-poor soil and chlorophyll retention around the leaf nodules is a common bioassay for cytokinins.
Abstract: In 6-month growth experiments it was found that leaf-nodulatedPsychotria mucronata seedlings grown in N-poor soil showed a restricted growth and developed severe nitrogen-deficiency symptoms in the leaves. Plants in the same soil supplied with NO3-N showed healthy growth and dark green leaves. Detached Psychotria leaves bearing leaf nodules exposed to an atmosphere containing N15-labelled nitrogen gas or acetylene gas gave no evidence of nitrogen fixation, either in the light or in the dark or in both in succession. Therefore nitrogen fixation is probably not associated with the leaf nodules.