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  • Nitrogen fixation  (63)
  • Springer  (63)
  • National Academy of Sciences
  • Periodicals Archive Online (PAO)
  • 1995-1999
  • 1985-1989  (36)
  • 1980-1984  (27)
  • 1955-1959
  • 1987  (36)
  • 1982  (27)
Collection
Publisher
  • Springer  (63)
  • National Academy of Sciences
  • Periodicals Archive Online (PAO)
Years
  • 1995-1999
  • 1985-1989  (36)
  • 1980-1984  (27)
  • 1955-1959
Year
  • 1
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    Springer
    Biology and fertility of soils 4 (1987), S. 61-66 
    ISSN: 1432-0789
    Keywords: Stem nodulation ; Aeschynomene afraspera ; Legume ; Nitrogen fixation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aeschynomene afraspera is a wild annual legume growing in periodically waterlogged soils in western Africa. This legume is characterized by a profuse stem nodulation. Nodules are formed on the stem at the emergence of lateral root primordia, called nodulation sites. These sites are irregularly distributed on vertical rows all along the stem and branches. Stem nodules are hemispherically shaped. Their outside is dark green and they contain a red-pigmented central zone. Stem nodules exhibit a high nitrogen-fixing potential. Acetylene reduction assays result in stem nodule activity of 309 μmol C2H4 g−1 dry nodule h−1. Field-grown stem nodulated Aeschynomene accumulated more N (51 g N m−2 in 10 weeks) than the root nodulated one. Because of this nitrogenfixing potential and its ability to grow in waterlogged conditions, A. afraspera could probably be introduced into tropical rice cropping systems.
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  • 2
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    Biology and fertility of soils 5 (1987), S. 83-87 
    ISSN: 1432-0789
    Keywords: Inoculation ; Inoculum dose ; Nitrogen fixation ; Chickpea ; Rhizobium spp. ; Cicer arietinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The influence of three inoculum rates on the performance of three chickpea (Cicer arietinum L.) Rhizobium strains was examined in the field on a Mollisol soil. Increasing amounts of inoculum improved the performance of the strains. A normal dose (104 cells per seed) applied at different intervals gave non-significant increases in nodulation, nitrogenase activity (acetylene reduction assay), nitrogen uptake and grain yield. A ten-fold increase in inoculum increased nodule number, shoot dry weight, nitrogenase activity (ARA) and grain yield, but increases over the control were significant only for nodule dry weight and nitrogen uptake by shoot and grain. The highest level of inoculum (100 × normal) significantly increased nodule dry weight, grain yield, total nitrogenase activity (ARA) and nitrogen uptake by shoot and grain. Strain TAL 620 was more effective than the other two. Combined nitrogen (60 kg N ha−1) suppressed nodulation and nitrogenase activity (ARA).
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  • 3
    ISSN: 1432-0789
    Keywords: Triticum aestivum ; T. turgidum ; Nitrogen fixation ; Field inoculation ; Acetylene reduction assay (ARA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar “Miriam” showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar “Miriam” to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.
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  • 4
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    Biology and fertility of soils 4 (1987), S. 15-19 
    ISSN: 1432-0789
    Keywords: Nitrogen fixation ; N-balance studies ; Azolla ; Blue-green algae ; Chemical N fertilization ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A nitrogen balance study conducted in ceramic pots under net house conditions for four seasons showed that flooded rice soil leaves a positive nitrogen balance (N increase) in soil after rice cropping in both fertilized and unfertilized soil. Recovery of nitrogen from rice soil was more than its input in unfertilized soil, but it was reverse in fertilized soil. Incorporation of Azolla or BGA twice as basal and 20 days after transplanting (DAT) alone or in combination showed higher nitrogen balance and N2-fixation (N gain) in soil than in that where it was applied once either as basal or 20 DAT. Planted soil showed more N2-fixation than that of fallow rice, and flooded soil fixed more nitrogen in comparison to non-flooded soil in light but less in dark. Soil exposed to light fixed more nitrogen than that of unexposed soil in both flooded and non-flooded conditions.
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  • 5
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    Biology and fertility of soils 4 (1987), S. 9-14 
    ISSN: 1432-0789
    Keywords: Rhizosphere ; Nitrogen fixation ; Root exudates ; Soil bacteria ; Carbon budget ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The association of rice seedlings (cv. Delta) with different strains of Azospirillum was studied under monoxenic conditions in the dark. Axenic 3-day-old seedlings were obtained on a C- and N-free medium and inoculated with 6 · 107 bacteria per plant in a closed vial. Seven days later, different components of a carbon budget were evaluated on them and on sterile controls: respired CO2, carbon of shoot and roots, bacterial and soluble carbon in the medium. Two strains (A. lipoferum 4B and A. brasilense A95) isolated from the rhizosphere of rice caused an increase in exudation, + 36% and + 17% respectively compared with sterile control. Shoot carbon incorporation and respiration were reduced by inoculation. A third strain (A. brasilense R07) caused no significant change in exudation. A. lipoferum B7C isolated from maize did not stimulate rice exudation either. We further investigated a possible effect of nitrogen fixation on this phenomenon: inhibition of nitrogen fixation by 10% C2H2 did not modify the extent of C exudation by rice associated with A. lipoferum 4B or with the non-motile A. lipoferum 4T.
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  • 6
    ISSN: 1432-2048
    Keywords: Alnus ; Ammonium ; Carbon translocation ; Endophyte damage ; Nitrogen fixation ; Root nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cloned plants of Alnus incana (L.) Moench were inoculated and grown without combined nitrogen for seven weeks. The effects of ammonium on the function and structure of the root nodules were studied by adding 20 mM NH4Cl (20 mM KCl=control) for four days. Nitrogenase activity decreased to ca. 50% after one day and to less than 10% after two days in ammonium treated plants, but was unaffected in control plants. The results were similar at photon flux densities of 200 and 50 μmol m-2 s-1. At the higher light level the effect was concentration dependent between 2 and 20 mM NH4Cl. The recovery was slow, and more than 11 d were needed for plants treated with 20 mM ammonium to reach initial activity. The distribution of 14C to the root nodules after assimilation of 14CO2 by the plants was not changed by the ammonium treatment. Microscopical studies of root nodules showed high frequencies of endophyte vesicles being visually damaged in nodules from ammonium-treated plants, but not in nodules from control plants. When nitrogenase activity was restored, visually damaged vesicles were again few, whereas young developing vesicles were numerous. The slow recovery, the 14C-translocation pattern, and the structural changes of the endophyte indicate a more complex mechanism of ammonium influence than simply a short-term reduction in supply of carbon compounds to the nodules.
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  • 7
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glycine ; Nitrogen fixation ; Proplastid ; Purine synthesis ; Root nodule ; Ureide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Subcellular organelle fractionation of nitrogen-fixing nodules of soybean (Glycine max (L.) Merr.) indicates that a number of enzymes involved in the assimilation of ammonia into amino acids and purines are located in the proplastids. These include asparagine synthetase (EC 6.3.1.1), phosphoribosyl amidotransferase (EC 2.4.2.14), phosphoglycerate dehydrogenase (EC 1.1.1.95), serine hydroxymethylase (EC 2.1.2.1), and methylene-tetrahydrofolate dehydrogenase (EC 1.5.1.5). Of the two isoenzymes of asparate aminotransferase (EC 2.6.1.1) in the nodule, only one was located in the proplastid fraction. Both glutamate synthase (EC 1.4.1.14) and triosephosphate isomerase (EC 5.3.1.1) were associated at least in part with the proplastids. Glutamine synthetase (EC 6.3.1.2) and xanthine dehydrogenase (EC 1.2.1.37) were found in significant quantities only in the soluble fraction. Phosphoribosylpyrophosphate synthetase (EC 2.7.6.1) was found mostly in the soluble fraction, although small amounts of it were detected in other organelle fractions. These results together with recent organelle fractionation and electron microscopic studies form the basis for a model of the subcellular distribution of ammonium assimilation, amide synthesis and uredie biogenesis in the nodule.
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  • 8
    ISSN: 1432-1939
    Keywords: Lupinus succulentus ; Fabaceae ; Lupine ; Quinolizidine alkaloids ; Nitrogen fixation ; Defoliation ; Plant-herbivore interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined the effects of nitrogen nutrition and defoliation on the alkaloids, nitrogen levels, and growth of Lupinus succulentus by growing plants under five nitrogen/defoliation treatments: 1) fertilization with a high-nitrate nutrient solution, 2) fertilization with a low-nitrate solution, 3) inoculation with N-fixing bacteria but without available soil nitrogen, 4) high-nitrate solution plus periodic partial defoliation, and 5) low-nitrate plus defoliation. In the absence of defoliation, plants from both the N-fixing and high-N treatments had higher concentrations of alkaloids and nitrogen, and higher growth rates than the low-N plants. Periodic defoliation had little effect on the high-N plants, but defoliated N-fixing plants were severely stunted and had lower alkaloid and nitrogen levels. The experimental treatments also affected the relative concentrations of the alkaloids. Our results indicate that 1) alkaloid composition and concentration in L. succulentus are determined by both nitrogen availability and developmental state, 2) plants relying solely on N-fixation respond quite differently to defoliation than those with adequate soil nitrogen, and 3) the food value of the plant tissue can be affected by an interaction between the effects of defoliation and nitrogen status.
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  • 9
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    Archives of microbiology 148 (1987), S. 286-291 
    ISSN: 1432-072X
    Keywords: Sulfate-reducing bacteria ; Desulfobacter species ; Acetate ; Hydrogen ; Autotrophic growth ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sulfate-reducing bacteria with oval to rod-shaped cells (strains AcRS1, AcRS2) and vibrio-shaped cells (strains AcRM3, AcRM4, AcRM5) differing by size were isolated from anaerobic marine sediment with acetate as the only electron donor. A vibrio-shaped type (strain AcKo) was also isolated from freshwater sediment. Two strains (AcRS1, AcRM3) used ethanol and pyruvate in addition to acetate, and one strain (AcRS1) grew autotrophically with H2, sulfate and CO2. Higher fatty acids or lactate were never utilized. All isolates were able to grow in ammonia-free medium in the presence of N2. Nitrogenase activity under such conditions was demonstrated by the acetylene reduction test. The facultatively lithoautotrophic strain (AcRS1), a strain (AcRS2) with unusually large cells (2×5 μm), and a vibrio-shaped strain (AcRM3) are described as new Desulfobacter species, D. hydrogenophilus, D. latus, and D. curvatus, respectively.
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  • 10
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    Archives of microbiology 149 (1987), S. 24-29 
    ISSN: 1432-072X
    Keywords: Frankia ; Nitrogen fixation ; Calcium ; Vesicle development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A calcium requirement was shown for both vesicle development and nitrogenase activity by Frankia strains EAN1pec and CpI1. Washing cells with EGTA or EDTA inhibited both vesicle development and nitrogenase activity. The inhibition of both was reversed by the addition of calcium. A variety of agents known to affect calcium-dependent biological processes, such as a Ca-ATPase inhibitor, Ca-channel blockers, Ca-ionophores, calmodulin antagonists and the local anaesthetics, tetracaine and dibucaine, inhibited nitrogenase activity. Respiratory studies showed that a CN-insensitive respiration process occurred only under nitrogen derepressing conditions. Respiration by NH4Cl-grown cells was completely inhibited by KCN while N2-grown cells were inhibited by only 70%. Removal of calcium ions by EGTA or by the addition of dibucaine or tetracaine blocked the CN-insensitive respiration. This CN-insensitive respiration may be involved in protecting nitrogenase inside the vesicles from oxygen.
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  • 11
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    Archives of microbiology 147 (1987), S. 383-388 
    ISSN: 1432-072X
    Keywords: Frankia ; Nitrogen fixation ; Vesicle development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between nitrogen fixation and development of a specialized cell structure, called the vesicle, was studied using four Frankia isolates. Nitrogenase activity was repressed in all four strains during growth with ammonia. Strain CpI1 formed no vesicles during NH4 growth. Strains ACN1 ag , EAN1pec and EUN1f produced low numbers of vesicles in the presence of ammonia. Following transfer to nitrogen-free media, a parallel increase in nitrogenase activity and vesicle numbers occurred with all four isolates. Appearance of nitrogenase activity was more rapid in those strains that possessed some vesicles at the time of shift to N2 as a nitrogen source. The ratio of vesicle numbers to level of nitrogenase activity varied widely among the four strains and in response to different growth conditions and culture age of the individual strains. Optimum conditions of temperature, carbon and energy source, nitrogen source and availability of iron and molybdenum were different for each of the four strains. Those conditions that significantly reduced nitrogenase activity were always associated with decreased numbers of vesicles.
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  • 12
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    Archives of microbiology 132 (1982), S. 219-224 
    ISSN: 1432-072X
    Keywords: Rhizobium ; Nitrogen fixation ; Nodules ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several mutants defective in nodulation were isolated from Rhizobium japonicum strains 3I1b110 and 61A 76. Mutants of class I do not form nodules after incubation with soybean [Glycine max (L.) Merrill] for 17 days, but will do so by 28 days. When host plants other than G. max are infected with several of these strains, there is no detectable difference in the time of nodulation or size of nodules as compared to the wild type. Two mutants of class I (i. e., SM1 and SM2) have been shown previously to be altered in the lipopolysaccharide portion of their cell wall. Mutants of class II are not slow to nodulate but form fewer nodules than the wild type on all the host plants tested. Mutants of class III are unable to form nodules. Some bacteriophage-resistant mutants, altered in cell surface structure, fall into this class. Two mutants of class III do not bind to soybean roots.
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  • 13
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    Archives of microbiology 133 (1982), S. 172-177 
    ISSN: 1432-072X
    Keywords: Beggiatoa ; Nitrogen fixation ; Acetylene reduction ; Nitrate assimilation ; Microaerobic ; Isolation of marine strains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four newly isolated marine strains of Beggiatoa and five freshwater strains were tested for nitrogen fixation in slush agar medium. All strains reduced acetylene when grown microaerobically in media containing a reduced sulfur source and lacking added combined nitrogen. The addition of 2 mmol N, as nitrate or ammonium salts, completely inhibited this reduction. Although not optimized for temperature or cell density, acetylene reduction rates ranged from 3.2 to 12 nmol·mg prot-1 min-1. Two freshwater strains did not grow well or reduce acetylene in medium lacking combined nitrogen if sulfide was replaced by thiosulfate. Two other strains grew well in liquid media lacking both combined nitrogen and reduced sulfur compounds but only under lowered concentrations of air. All freshwater strains grew well in medium containing nitrate as the combined nitrogen source. Since they did not reduce acetylene under these conditions, we infer that they can assimilate nitrate.
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  • 14
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    Archives of microbiology 133 (1982), S. 312-317 
    ISSN: 1432-072X
    Keywords: Rhizobium japonicum ; Rhizobium leguminosarum ; Formate metabolism ; Formate dehydrogenase ; Nitrogen fixation ; Nitrogenase ; Bacteroids ; Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Formate metabolism supported nitrogen-fixation activity in free-living cultures of Rhizobium japonicum. However, formate0dependent nitrogense activity was observed only in the presence of carbon sources such as glutamate, ribose or aspartate which by themselves were unable to support nitrogenase activity. Formate-dependent nitrogenase activity was not detected in the presence of carbon sources such as malate, gluconate or glycerol which by themselves supported nitrogenase activity. A mutant strain of R. japonicum was isolated that was unable to utilise formate and was shown to lack formate dehydrogenase activity. This mutant strain exhibited no formate-dependent nitrogenase activity. Both the wild-type and mutant strains nodulated soybean plants effectively and there were no significant differences in the plant dry weight or total nitrogen content of the respective plants. Furthermore pea bacteroids lacked formate dehydrogenase activity and exogenously added formate had no stimulatory effect on the endogenous oxygen uptake rate. The role of formate metabolism in symbiotic nitrogen fixation is discussed.
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  • 15
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    Archives of microbiology 146 (1987), S. 327-331 
    ISSN: 1432-072X
    Keywords: Actinomycetes ; Nitrogen fixation ; Symbiosis ; Immunocytochemistry ; Ultracryotomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Immunogoldlabelling on ultrathin cryosections of Frankia sp. Cc1.17 showed specific labelling of nitrogenase in the spherical cells called vesicles. No label was found in the hyphae in any cells grown on a medium with combined nitrogen, nor in those to which no specific antiserum was added. Similar results were obtained with cultures grown under high (20%) and low (2%) oxygen tension in the gas phase.
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  • 16
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    Archives of microbiology 132 (1982), S. 333-337 
    ISSN: 1432-072X
    Keywords: Anabaena variabilis Kütz ; 14C-prelabeled blue-green algae ; Interaction respiration/photosynthesis ; CO2 exchange ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Prelabeled Anabaena variabilis Kütz. evolves 14CO2 in the light with KCN and DCMU (2,4-dichlorophenyl-1,1-dimethylurea) present, comparable to the dark control without inhibitors added. Double-reciprocal plots of CO2 release vs. light intensity with either KCN or KCN+DCMU present result in two straight lines intersecting at the ordinate. Apparently, reducing equivalents originating from carbohydrate catabolism are channeled into the photosynthetic electron-transport chain, competing for electrons from photosystem II. Under these conditions, the CO2 release is accompanied by a light-dependent oxygen uptake, presumably due to oxygen-reducing photosystem-I activity while ribulose-bisphosphate carboxylase is inhibited by KCN. Comparing nine blue-green algae it was shown that only nitrogen-fixing species release substantial amounts of CO2 in the light with KCN or KCN+DCMU present. This release is particularly obvious with Anabaena variabilis Kütz. under nitrogen-fixing conditions, but small when the alga is grown with combined nitrogen. We conclude that nitrogen-fixing species share a common link between respiratory and photosynthetic electron transport. The physiological role may be electron supply of nitrogenase by photosystem I.
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  • 17
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    Archives of microbiology 133 (1982), S. 6-10 
    ISSN: 1432-072X
    Keywords: Rhodospirillaceae ; Rhodopseudomonas globiformis ; Nitrogen metabolism ; Nitrogen fixation ; Glutamine synthetase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rhodopseudomonas globiformis strain 7950 grew with a variety of amino acids, urea, or N2 as sole nitrogen sources. Cultures grown on N2 reduced acetylene to ethylene; this activity was absent from cells grown on nonlimiting NH 4 + . Glutamate dehydrogenase could not be detected in extracts of cells of strain 7950, although low levels of an alanine dehydrogenase were present. Growth ofR. globiformis on NH 4 + was severely inhibited by the glutamate analogue and glutamine synthetase inhibitor, methionine sulfoximine. High levels of glutamine synthetase (as measured in the γ-glutamyl transferase assay) were observed in cell extracts of strain 7950 regardless of the nitrogen source, although N2 and amino acid grown cells contained somewhat higher glutamine synthetase contents than cells grown on excess NH 4 + . Levels of glutamate synthase inR. globiformis were consistent with that reported from other phototrophic bacteria. Both glutamate synthase and alanine dehydrogenase were linked to NADH as coenzyme. We conclude thatR. globiformis is capable of fixing N2, and assimilates NH 4 + primarily via the glutamine synthetase/glutamate synthase pathway.
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  • 18
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    Theoretical chemistry accounts 60 (1982), S. 579-587 
    ISSN: 1432-2234
    Keywords: Nitrogen fixation ; Nitrogen complexes ; Carbon monoxide complexes ; Electronic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract MNDO method is used to study the interaction of nitrogen and carbon monoxide molecules with a proton, hydrogen atom, hydride ion, hydrogen molecule ion and hydrogen molecule. Predicted geometries and heats of reaction of different complexes are presented. The wave functions are analyzed in terms of ground state charge distributions and overlap populations. Electronic effects accompanying complexation are also discussed.
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  • 19
    ISSN: 1476-5535
    Keywords: Sulfate-reducing bacteria ; Hydrogen metabolism ; Nitrogen fixation ; Deuterium-proton exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D2−H+ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism.
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  • 20
    ISSN: 1432-2048
    Keywords: Nitrogen fixation ; Peroxisome ; Root nodules ; Ureide biogenesis ; Uricase ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cowpea (Vigna unguiculata (L.) Walp.) nodules have been investigated by means of cytochemical and immunocytochemical procedures at the ultrastructural level in order to assess the role of the uninfected cells in ureide biogenesis. Uricase activity in the nodules was shown by cytochemical methods to be localized exclusively in the numberous large peroxisomes confined to the uninfected cells; the small peroxisomes in the infected cells did not stain for uricase. Uricase was also localized in the peroxisomes of uninfected cells by immunogold techniques employing polyclonal antibodies against nodule-specific uricase of soybean. There was no labeling above background of any structures in the infected cells. The results indicate that the uninfected cells are essential for ureide biogenesis in cowpea. Although tubular endoplasmic reticulum, the presumptive site of allantoinase, increases greatly in the uninfected cells during nodule development, it virtually disappears as the nodules mature. The inconsistency between the disappearance of the tubular endoplasmic reticulum from older nodules and the high allantoinase activity reported for older plants remains to be explained.
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  • 21
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    Molecular genetics and genomics 208 (1987), S. 481-484 
    ISSN: 1617-4623
    Keywords: PEP carboxylase ; Azotobacter chroococcum ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Azotobacter chroococcum Fos 189 is a Tn1-induced mutant which, unlike the parent strain MCD1, does not fix nitrogen in air when provided with glucose or pyruvate as sole carbon sources. Fos 189 showed 5% of parental activity for phosphoenolpyruvate carboxylase though PEP synthetase activity was normal. The A. chroococcum phosphoenolpyruvate carboxylase (ppc) gene was isolated after complementation of an appropriate Escherichia coli mutant using a broad host range gene bank prepared from A. chroococcum genomic DNA. The gene was localised by transposon mutagenesis and subcloning on a minimum DNA fragment of 6.6 kb. Broad host range plasmids containing the A. chroococcum ppc gene complemented the mutation in Fos 189 thereby restoring aerotolerant nitrogen fixation.
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  • 22
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    Molecular genetics and genomics 207 (1987), S. 503-508 
    ISSN: 1617-4623
    Keywords: Bradyrhizobium ; Nif genes ; Nitrogen fixation ; Root nodule symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 17 kb region between the Bradyrhizobium japonicum nitrogenase genes (nifDK and nifH) was investigated for the presence of further nif or fix genes by site-directed insertion or deletion/replacement mutagenesis and interspecies hybridization. Mutant strains were tested for their ability to reduce acetylene in free-living, microaerobic culture (Nif phenotype) and in soybean root nodules (Fix phenotype). The presence of a gene, previously identified by hybridization with the Klebsiella pneumoniae nifB gene, was proved by isolation of a nifB insertion mutant which was completely Nif- and Fix-. Three other regions were found to be homologous to the K. pneumoniae genes nifE, nifN, and nifS, NifE and nifN insertion mutants were completely Nif-/Fix- whereas nifS mutants were leaky with 30% residual Fix activity. Taken together, the data show that the B. japonicum genome harbours a cluster of closely adjacent genes which are directly concerned with nitrogenase function.
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  • 23
    ISSN: 1617-4623
    Keywords: Azorhizobium sesbaniae ORS571 ; Nitrogen fixation ; Regulation ; Tn5 mutagenesis ; lacZ fusions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cosmid bank of ORS571, a diazotrophic bacterium capable of inducing aerial stem and root nodules on Sesbania rostrata, was constructed in the vector pLAFR1. A DNA probe carrying the Klebsiella pneumoniae nifA gene was used to identify nifA-and ntrC-like regions of ORS571 in the cosmid bank by colony hybridization. Cosmids carrying these regions were mapped by restriction endonuclease analysis, Southern blotting and transposon Tn5 mutagenesis. Selected Tn5 insertion mutations in the nifA/ntrC homologous regions were used for gene-replacement experiments and the resulting ORS571 mutants were examined for Nif, Fix and Ntr phenotypes. Two clearly distinct regulatory loci were thus identified and named nifA and ntrC. Plasmids carrying gene fusions of the ORS571 nifH and nifD genes to lacZ were constructed and the regulation of the ORS571 nifHDK promoter, and of the Rhizobium meliloti nifHDK promoter, was studied under varying physiological conditions in ORS571, ORS571 nifA::Tn5 and ORS571 nitrC::Tn5 strains. A model for the role of nifA and ntrC in the regulation of ORS571 nif and other nitrogen assimilation genes is proposed.
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  • 24
    ISSN: 1617-4623
    Keywords: Gene regulation ; Melanin synthesis ; Nitrogen fixation ; Phaseolus beans ; Rhizobium phaseoli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The symbiotic plasmid pRP2JI of Rhizobium phaseoli strain 8002 was shown to contain two separate regions of DNA which are required and sufficient for the synthesis of the pigment melanin. One of these regions containing the class II mel gene(s) was located to other genes involved in nodulation and in nitrogen fixation. Mutations in this region abolished both the ability to synthesize melanin and to fix nitrogen in Phaseolus bean root nodules. Mutations in the other, unlinked region, containing class I mel gene(s), also abolished melanin synthesis but did not affect symbiotic nitrogen fixation. Transcriptional fusions between the class I mel gene and the Escherichia coli lacZ gene were constructed and it was demonstrated that the class II mel gene(s) activated their transcription in free-living culture. Further, strains containing the cloned regulatory class II gene(s) synthesized melanin when growing in minimal medium, in contrast to wild-type strains which became pigmented only in complete medium containing yeast extract and tryptone. It was shown by hybridization experiments that the regulatory mel gene was closely linked to or may correspond to the regulatory nifA gene; a fragment of R. phaseoli DNA which included the class II gene(s) of R. phaseoli hybridized to a previously identified nifA-like gene of R. leguminosarum, the species that nodulates peas.
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  • 25
    ISSN: 1617-4623
    Keywords: Agrobacterium rhizogenes ; Plant transformation ; Transgenic legumes ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A procedure for transformation and regeneration of the legume species Lotus corniculatus (Bird's-foot trefoil) has been developed. The Agrobacterium rhizogenes 15834 and 8196 strains were used to transform plant cells in wound site infections and transformed roots were propagated in vitro. Transformation was monitored by hybridization with pRi T-DNA sequences and by detection of agropine and mannopine. Transformation frequencies of up to 90% were obtained. Shoots spontaneously formed on hairy root cultures were excised, rooted and inoculated with Rhizobium. Root nodules formed on transformed plants had nitrogenase activities comparable to untransformed nodules. Transcript levels from the nodule-specific leghemoglobin genes and the constitutive ubiquitin genes were similar in transformed and untransformed root nodules. Transformed plants responded to R. loti and Bradyrhizobium sp. (Lotus) strains with phenotypes identical to phenotypes for untransformed plants.
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  • 26
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    Molecular genetics and genomics 206 (1987), S. 291-299 
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; Stem nodulation ; Tn5 mutagenesis ; nod genes ; nodC homology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary After random Tn5 mutagenesis of the stem-nodulating Sesbania rostrata symbiont strain ORS571, Nif-, Fix- and Nod- mutants were isolated. The Nif- mutants had lost both free-living and symbiotic N2 fixation capacity. The Fix- mutants normally fixed N2 in the free-living state but induced ineffective nodules on S. rostrata. They were defective in functions exclusively required for symbiotic N2 fixation. A further analysis of the Nod- mutants allowed the identification of two nod loci. A Tn5 insertion in nod locus 1 completely abolished both root and stem nodulation capacity. Root hair curling, which is an initial event in S. rostrata root nodulation, was no longer observed. A 400 bp region showing weak homology to the nodC gene of Rhizobium meliloti was located 1.5 kb away from this nod Tn5 insertion. A Tn5 insertion in nod locus 2 caused the loss of stem and root nodulation capacity but root hair curling still occurred. The physical maps of a 20.5 kb DNA region of nod locus 1 and of a 40 kb DNA region of nod locus 2 showed no overlaps. The two nod loci are not closely linked to nif locus 1, containing the structural genes for the nitrogenase complex (Elmerich et al. 1982).
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  • 27
    ISSN: 1617-4623
    Keywords: Bradyrhizobium japonicum ; Transposon Tn5 ; Mutants ; Nodulation ; Nitrogen fixation
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    Topics: Biology
    Notes: Summary Two strains of the soybean endosymbiont Bradyrhizobium japonicum, USDA 110 and 61 A101 C, were mutagenized with transposon Tn5. After plant infection tests of a total of 6,926 kanamycin and streptomycin resistant transconjugants, 25 mutants were identified that are defective in nodule formation (Nod-) or nitrogen fixation (Fix-). Seven Nod- mutants were isolated from strain USDA 110 and from strain 61 A101 C, 4 Nod- mutants and 14 Fix- mutants were identified. Subsequent auxotrophic tests on these symbiotically defective mutants identified 4 His- Nod- mutants of USDA 110. Genomic Southern analysis of the 25 mutants revealed that each of them carried a single copy of Tn5 integrated in the genome. Three 61 A101 C Fix- mutants were found to have vector DNA co-integrated along with Tn5 in the genome. Two independent DNA regions flanking Tn5 were cloned from the three nonauxotrophic Nod- mutants and one His-Nod- mutant of USDA 110. Homogenotization of the cloned fragments into wild-type strain USDA 110 and subsequent nodulation assay of the resulting homogenotes confirmed that the Tn5 insertion was responsible for the Nod- phenotype. Partial EcoR1 restriction enzyme maps around the Tn5 insertion sites were generated. Hybridization of these cloned regions to the previously cloned nod regions of R. meliloti and nif and nod regions of B. japonicum USDA 110 showed no homology, suggesting that these regions represent new symbiotic clusters of B. japonicum.
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  • 28
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    Molecular genetics and genomics 206 (1987), S. 460-464 
    ISSN: 1617-4623
    Keywords: Agrobacterium tumefaciens ; Klebsiella pneumoniae ; Nitrogen fixation ; Gene fusions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plasmids containing hybrid genes, in which different Klebsiella pneumoniae nif (nitrogen-fixation) promoters were fused with the structural part of the Escherichia coli lac operon, were introduced into a double auxotrophic derivative of Agrobacterium tumefaciens C58. A study of their expression in the new host was made simple by the inherent inability of A. tumefaciens C58 to produce β-galactosidase unless provided with the wild-type lac operon of E. coli. As shown by quantitative measurements of the enzyme, all K. pneumoniae promoters were expressed well in A. tumefaciens C58, even under conditions known to repress them. It also has been shown that the activity of K. pneumoniae nif A is essential for the expression of nifHDK even when introduced into A. tumefaciens. After entering the new host the plasmids, the nif genes and the fusion alleles contained in them, remained stable. Possible mechanisms responsible for the constitutive behaviour of nif promoters in A. tumefaciens are discussed.
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  • 29
    ISSN: 1617-4623
    Keywords: Beans ; DNA Sequence ; Gene regulation ; Nitrogen fixation ; Nodulation ; Rhizobium
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    Topics: Biology
    Notes: Summary A gene termed psi (polysaccharide inhibition), located close to the nodulation genes of the Rhizobium phaseoli symbiotic plasmid pRP2JI inhibited exopolysaccharide synthesis (EPS) and nodulation ability (Nod) in Rhizobium when it was cloned in a multicopy plasmid. The sequence of psi showed that it specified a polypeptide of mol. wt. 10000 that may be associated with the membrane of Rhizobium. A second gene, psr (polysaccharide restoration), was located on pRP2JI. When cloned in multicopy plasmids, psr overcame the EPS and Nod defects in strains carrying multicopy psi. Strains with multicopy psr induced non-fixing nodules on Phaseolus beans. Using gene fusions between psi and lacZ, it was shown that psi inhibited transcription of psr.
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    Molecular genetics and genomics 207 (1987), S. 280-287 
    ISSN: 1617-4623
    Keywords: Rhizobium ; Nitrogen fixation ; Nif products ; Tn5 mutagenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Deletions and Tn5 insertions were obtained in a cloned 10 kb BamHI-BglII fragment carrying the nifHDKE region of Rhizobium ORS571 and were recombined into the host genome. Genetic analysis of the mutants, comparison of polypeptides synthesized under conditions of repression and depression of N2 fixation, and biochemical complementation of crude extracts were performed. All Nif- mutants were also Fix-. Three transcription units were identified, nifHDK, nifE and a new nif locus adjacent to nifE; no nif locus was found in the immediate vicinity upstream of nifH. Fifteen polypeptides synthesized under conditions of N2 fixation were characterized by two-dimensional gel electrophoresis. Ten of them are likely to be nif products and polypeptides encoded by nifH, nifD, nifK and tentatively nifE were identified. Physiological and biochemical evidence for the functioning of the second copy of nifH is reported. Nitrogenase component 2 synthesized by this copy could not be differentiated from component 2 synthesized in the wild-type strain. When the function of nifH copy 1 was abolished, the amount of component 2 synthesized was about 30% of that synthesized in the wild-type strain.
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  • 31
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    Molecular genetics and genomics 209 (1987), S. 621-626 
    ISSN: 1617-4623
    Keywords: Bradyrhizobium japonicum ; nifA gene ; Nitrogen fixation ; Oxygen control ; Transcriptional control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The nifA genes of Klebsiella pneumoniae and Bradyrhizobium japonicum were constitutively expressed from the pBR329-derived chloramphenicol resistance promoter. The inserts of these nifA plasmid constructs were devoid of any other intact flanking genes. The nifA genes thus expressed led to a marked activation of a B. japonicum nifD-lacZ fusion under microaerobic conditions. Under aerobic growth conditions, however, activation was mediated only by the K. pneumoniae nifA gene but not by the B. japonicum nifA gene. This selective effect was observed in both the Escherichia coli as well as the B. japonicum backgrounds. Several lines of evidence suggest that in these experiments oxygen adversely affects B. japonicum nifA-dependent nif gene regulation at the post-transcriptional level, probably even at the post-translational level, and that this effect does not require a nifL-like gene. Models are proposed in which oxygen inhibits the B. japonicum NifA protein either directly or indirectly via other cellular components involved in general protein oxidation pathways.
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  • 32
    ISSN: 1573-5036
    Keywords: Drought stress ; Nitrogen fixation ; Nodulation ; Prosopis spp ; Semi-arid ; Tree legumes ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The literature does not contain a field report of nodulation for the xerophytic tree legumes of the genus Prosopis despite their widespread occurrence in semi-arid regions of the world. A phraetophytically simulated greenhouse experiment was conducted with mesquite in a 3m deep soil column to determine if nodules would form in deper depths where moisture is more abundant. The upper 0.5m in the soil column was allowed to dry to 2200 kPa but the 3.2 m depth was maintained at soil moistures more positive than 70 kPa by water additions to the bottom of the soil column. Over 100 nodules and an acetylene reduction rate of 1.9 mg/h were observed at the 3.2m depth. Nodulation or acetylene reduction were not observed closer than 2.7m from the surface. Air temperatures during these assays exceeded 45°C. Leaf xylem water potentials were in the 2800–3500 kPa range.
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  • 33
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    Plant and soil 65 (1982), S. 383-396 
    ISSN: 1573-5036
    Keywords: Frankia ; Microbial ecology ; Nitrogen fixation ; Purshia ; Revegetation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen fixing trees and shrubs may be useful in revegetation efforts. Speculation that insufficient endophyte populations in surface soils may limit non-leguminous symbiotic nitrogen fixation in marginal land was explored.Purshia tridentata andP. glandulosa seedlings were grown in greenhouse trials using ten soils from nativePurshia sites. Treatments include a control, an inoculated treatment, and six mmole nitrogen amendment. When inoculated with aP.tridentata crushed nodule inoculum, two of five non-nodulating soils and three sparsely nodulating soils produced well nodulated plants. Inoculation also increased nodule mass, total nitrogen, nitrogen content and shoot dry mass in plants from some of the soils. Of the three soils failing to produce nodulated plants when inoculated, one produced plants that responded well to nitrogen additions but failed to nodulate under low nitrogen conditions; another produced severely stunted plants indicating nutritional limitations on the host; and the third produced plants that were not nitrogen deficient. An application of nitrogen completely suppressed nodulation in all but one soil. The twoPurshia species were similar in nodulation, nitrogen fixation and growth, although important exceptions exist that indicate species may differ in adaptability to certain soil conditions.
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  • 34
    ISSN: 1573-5036
    Keywords: Acridine orange ; Cochliobolus sativus ; Common root rot ; Nitrogen fixation ; Nuclear staining ; Roots ; Senescence ; Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Natural senescence of the root cortex was assessed by nuclear staining, for cultivars and chromosome substitution lines of spring wheat known to differ in (1) susceptibility to common root rot, (2) total rhizosphere populations and (3) ability to support growth of a free-living nitrogen-fixing bacterium. Together, three root rot susceptible wheat lines showed significantly more cortical senescence than did three resistant lines; the susceptible lines also support larger rhizosphere populations. The wheat line that supports growth of a nitrogen-fixing bacterium showed significantly less cortical death than did any other line. Substitution of chromosome pairs 5B or 5D between the parent cultivars Rescue and Cadet substantially altered the amount of root cortex death, which is thus genetically determined. It is suggested thatCochliobolus sativus and other weak parasites benefit from early natural senescence of the root cortex, and that the degree of susceptibility or resistance of wheat lines to common root rot is at least partly determined by differences in cortical senescence.
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  • 35
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    Plant and soil 68 (1982), S. 55-67 
    ISSN: 1573-5036
    Keywords: Klebsiella ; Nitrogen fixation ; Oryza sativa ; Phyllosphere ; Rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The beneficial effect of spraying some highly active phyllosphere N2-fixing microorganisms on high and low yielding cultivars of rice plants as compared with that of urea applied at different doses are described. The dry weight, N-content, 1000 grain weight, and yield were remarkably increased in all cases with the application of phyllosphere microorganisms. The performance of two isolates KUP4 and KUPBR2 with IR-8 and IR-26 rice, was better than that of 52 kg urea-N per hectare. IR-579 rice leaves in association with some phyllosphere bacteria reduced acetylene at the rate of 664–816 nmoles/g leaf/h. In IR-26 rice the effect of application of bacterial suspension at three phases of plant growth corresponded very well with that of urea application in three split doses under identical conditions. Recommended fertilizer rates produced the same yield as the half dose plus bacterial spray in the cultivars Pankaj and Rupsail. Fertilizer application in Pankaj and Rupsail rice reduced nitrogenase activity and the beneficial effects of phyllosphere N2-fixation was reduced by 40–55%.
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  • 36
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    Plant and soil 69 (1982), S. 233-238 
    ISSN: 1573-5036
    Keywords: Nitrogen fixation ; Azospirillum spp. ; Azospirillum lipoferum ; Wheat yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Seven isolates belonged toA. brasilense and 3 belonged toA. lipoferum. Isolates having more denitrifying capacity fixed less nitrogen in nitrogen free semi-solid malate medium. One strain ofA. lipoferum having high nitrogen fixing capacity with negative test for denitrification was tested as inoculant to supplement the nitrogen need of a wheat crop in field condition with different doses of N with and without the inoculant. While control without nitrogen yielded 1260 kg/ha the yield in inoculated treatment was 2070 kg/ha resulting in significant increase. In a treatment receiving 40 kg N/ha the grain yield was 2370 kg/ha as against yield of 3110 kg/ha in a similar treatment receiving fertiliser plus inoculant. Thus increase in yield was about 30%. Further the treatment receiving 80 kg N/ha yielded 2970 kg/ha as against yield of 4150 kg/ha in a treatment receiving inoculant alongwith the above dose of the fertiliser. Thus increase in yield due to application of inoculant was about 36%. Similarly, the uptake of N in different treatments was augmented due to inoculation of seeds with the culture.
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  • 37
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    Plant and soil 69 (1982), S. 293-297 
    ISSN: 1573-5036
    Keywords: Ecology ; Frankia ; Nitrogen fixation ; Water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Growth responses of Frankia isolates to decreasing water potential were monitored in systems where potentials were controlled by KCl, NaCl and Polyethylene glycol. The highest potential tested was −2 bar (basal medium). The general pattern emerging was that isolates fromAlnus glutinosa, A. viridis andComptonia peregrina showed declining growth at potentials below −2 to −5 bar. AMyrica gale isolate showed declining growth with decreasing potential. All isolates were more sensitive to decreases in potential in a matric controlled than an osmotic controlled system. They all showed approximately 50 percent growth reduction at −5 to −8 bar, and meagre growth at −16 bar after 35 days. The Comptonia isolate was the most vigorous at low potentials. Nitrogen fixation ability was monitored for two isolates. Highest specific activities were observed between −3 and −5 bar for the Myrica isolate and between −5 and −7.5 bar for theA. glutinosa isolate.
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  • 38
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    Plant and soil 69 (1982), S. 341-352 
    ISSN: 1573-5036
    Keywords: Barley ; Nitrogen fixation ; Rhizoplane ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Aerobic and anaerobic N2-fixing bacteria developed in the rhizosphere of barley seedlings and exhibited N2ase activity when seedlings were grown in sterilized sand-nutrient cultures containing low levels of combined nitrogen. The source of the N2-fixing bacteria appeared to be the seed. Average daily rates up to 0.9 μmoles C2H4 h−1 g−1 dry root tissue were measured, but the intensity of the activity was affected by moisture levels and concentration of combined N in the rhizosphere. Removal and washing of the roots did not remove the activity, and roots remained active even after surface-sterilization. An unidentified aerobic N2-fixing bacterium was isolated from the rhizoplane of active barley roots. Inoculation of barley seedlings with the aerobic N2-fixing bacterium enhanced N2ase activity of excised roots 10-fold, with average rates of 0.9, 1.1 and 1.3 μmoles h−1 g−1 dry root assayed under pO2 of 0.01, 0.02 and 0.04 atm respectively. The aerobic N2-fixing bacterium also exhibited N2ase activity when inoculated into the rhizosphere of oat, rice and wheat seedlings. Microscopic observations of sterilized live and stained barley roots suggest that the aerobic N2-fixing bacterium is an endophyte which infects root tissue and metamorphoses into vesicle-like structures.
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  • 39
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    Plant and soil 100 (1987), S. 225-236 
    ISSN: 1573-5036
    Keywords: Actinorhizae ; Alnus ; Casuarina ; Frankia ; Hemoglobin ; Myrica ; Nitrogen fixation ; Root nodules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The concentration of total and CO-reactive heme was measured in actinorhizal nodules from six different genera. This gave the upper limit to hemoglobin concentration in these nodules. Quantitative extraction of CO-reactive heme was achieved under anaerobic conditions in a buffer equilibrated with CO and containing Triton X-100. The concentration of CO-reactive heme in nodules of Casuarina and Myrica was approximately half of that found in legume nodules, whereas in Comptonia, Alnus and Ceanothus the concentrations of heme were about 10 times lower than in legume nodules. There was no detectable CO-reactive heme in Datisca nodules, but low concentrations were detected in roots of all non-nodulating plants examined, includingZea mays. Difference spectra of CO treated minus dithionite-reduced extracts displayed similar wavelengths of maximal and minimal light absorption for all extracts, and were consistent with those of a hemoglobin. The concentration of CO-reactive heme was not correlated to the degree to which CO inhibited nitrogenase activity nor was it affected by reducing the oxygen concentration in the rooting zone. However, there was a positive correlation between heme concentration and suberization or lignification of the walls of infected host cells. These observations demonstrate that, unlike legume nodules, high concentrations of heme or hemoglobin are not needed for active nitrogen fixation in most actinorhizal nodules. Nonetheless, a significant amount of CO-reactive heme is found in the nodules of Alnus, Comptonia, and Ceanothus, and in the roots ofZea mays. The identity and function of this heme is unknown.
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  • 40
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    Plant and soil 64 (1982), S. 251-253 
    ISSN: 1573-5036
    Keywords: Competition of Rhizobium ; Nitrogen fixation ; Nodulation ; Vigna radiata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Competition of five strains of Rhizobium of the cowpea group, onVigna radiata (L) Wilcjeck variety ML 5, was tested in loamy clay and loamy sand soils. Strains RM 6 and RM 5 were effective nodulators in loamy clay soil, and strains MNH, M 20 and RM 6 were effective nodulators in loamy sand soil. Strains RM 6 and MNH predominated nodule formation in loamy clay and loamy sand soils respectively.
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  • 41
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    Plant and soil 64 (1982), S. 263-266 
    ISSN: 1573-5036
    Keywords: Blue-green algae ; Nitrogen fertilisers ; Nitrogen fixation
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    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of ammonium or nitrate-nitrogen on biological nitrogen fixation by an algal crust are compared. Nitrate-nitrogen up to 3.0 μmoles N g−1 sand/algal crust at 60% water holding capacity did not affect fixation, whereas an ammonium-nitrogen concentration of 0.2 μmoles N g−1 crust markedly depressed fixation. Consequences of these differential effects are considered.
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  • 42
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    Plant and soil 66 (1982), S. 21-28 
    ISSN: 1573-5036
    Keywords: Agro-forestry ; Acetylene reduction ; Leucaena leucocephala ; Nematode root knots ; Nitrogen fixation ; Nodule biomass ; Woody legume
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The nitrogen fixation rate in a 4-year-old stand of the woody legumeLeucaena leucocephala (Lam.) de Wit. was estimated in the field at a rather dry site in Tanzania by use of an acetylene reduction technique. The diurnal mean value during April–May was 35 nmol C2H4 mg−1 (dry weight) nodules h−1, with a variation between 22±8 and 48±12 nmol C2H4 mg−1 (dry weight) nodules h−1 in early morning and at midday, respectively. The nodule biomass was determined by auger sampling to be 51±16 kg (dry weight) ha−1. Most of the nodules were found at the 10–30 cm soil depth level. A rough calculation of the amount of nitrogen fixed annually arrived at 110±30 kg ha−1. The results give strong support for the use ofL. leucocephala for soil enrichment in less humid areas of tropical Africa.
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  • 43
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    Plant and soil 66 (1982), S. 125-127 
    ISSN: 1573-5036
    Keywords: Charcoal ; Garden pea ; Inoculation ; Nitrogen fertilisation ; Nitrogen fixation ; Nodulation ; Pisum sativum ; Wood charcoal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In a factorial pot experiment on garden peas investigating the effect of growing medium, inoculation, nitrogen fertilisation and charcoal addition, shoot growth was significantly better in John Innes potting compost than in 50/50 peat/sand compost and when receiving nitrogen fertilisation but was depressed by the presence of wood charcoal. In the peat/sand medium, root systems were smaller but carried more and larger nodules. The number of nodules was increased by inoculation but the addition of carbon decreased root size, nodule number and nodule size.
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  • 44
    ISSN: 1573-5036
    Keywords: Aluminium toxicity ; Nitrogen fixation ; Nodulation ; Stylosanthes hamata ; Stylosanthes humilis ; Stylosanthes scabra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Effects of three solution aluminium concentrations (0, 25, and 100μM) on nitrogen fixation by well-nodulated plants ofStylosanthes hamata, Stylosanthes humilis andStylosanthes scabra are reported. Plants were inoculated with Rhizobium CB756 and grown for 21 days in an aluminium-free nutrient solution at pH 5.3 before imposition of the aluminium treatments. Nitrogen fixation was measured both by the increase in total nitrogen content of the plants and acetylene reduction in roots of plants harvested at 10 and 20 days after imposition of the aluminium treatments. Solution aluminium concentrations as high as 100μM, had no detrimental effect on nitrogen fixation in any species.
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  • 45
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    Plant and soil 66 (1982), S. 413-416 
    ISSN: 1573-5036
    Keywords: Growth ; Nematicide ; Nitrogen fixation ; Nodulation ; Peanut ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of two granular nematicidesviz. oxamyl and fenamiphos, on the nodulation and growth of Rhizobium inoculatedArachis hypogaea L. was studied in glasshouse and field trials. In the glasshouse trial at the suggested rates of application shoot fresh weight was significantly reduced by oxamyl whilst root fresh weight was similarly affected by fenamiphos. In the field trial vegetative growth and plant emergence were significantly reduced by both nematicides. Nodulation at the higher rates of application was increased by both oxamyl and fenamiphos whilst oxamyl caused a significant increase in pod number at the highest rate of application.
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  • 46
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    Plant and soil 68 (1982), S. 321-329 
    ISSN: 1573-5036
    Keywords: Alginate ; A value ; Endomycorrhiza ; Glomus mosseae ; Inoculant ; Nitrogen fixation ; Rhizobium japonicum ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This field study was undertaken to determine the effect of inoculation withGlomus mosseae on N2 fixation and P uptake by soybean. The inoculation withGlomus mosseae was achieved using a new type of inoculant, alginate-entrapped (AE) endomycorrhizal fungus. N2 fixation was assessed using the A value method. In P-fertilized plots, inoculation with AEGlomus mosseae increased the harvest index based on dry weight (+20%) and N content of seeds (+17%), the A value (+31%) and %N derived from fixation (+75%). Inoculation with AEGlomus mosseae decreased the coefficient of variation for the A value and for the dry weights of the different plant parts.
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  • 47
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    Plant and soil 69 (1982), S. 265-273 
    ISSN: 1573-5036
    Keywords: Azotobacter chroococcum ; Fertilizers ; Farmyard manure ; Nitrogen ; Nitrogen fixation ; Potassium ; Phosphorus ; Yields of grain stover ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field trials were conducted during theKharif seasons of 1979 and 1980 to examine the effect of the nitrogen-fixing bacteriumAzotobacter chroococcum (isolate M4) on yields of maize and N-economy. Different levels of nitrogen and farmyard manure (FYM) were supplied to assess their interaction with Azotobacter inoculation. Seed inoculation without fertilization raised grain and stover yields significantly. FYM coupled with inoculation gave higher yields than either could singly. The financial gain due to an increase in grain yield upon applying per ha 80 kg N, 10×103 kg FYM and Azotobacter over the treatment 40N + FYM + Azotobacter was offset by the cost of the additional N; thus, the higher N-application was not economical. Azotobacter inoculation was economically most efficient at lower doses of fertilizer nitrogen which not only increased yields but resulted in a saving of fertilizer N when applied in combination with FYM.
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  • 48
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    Plant and soil 69 (1982), S. 275-280 
    ISSN: 1573-5036
    Keywords: Azotobacter chroococcum ; Fertilizers ; Farmyard manure ; Zea mays ; Maize ; Nitrogen ; Nitrogen fixation ; Phosphorus ; Potassium ; Total nitrogen uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The economic feasibility of using cultures of nitrogen fixing microorganisms in programmes to increase crop production, as a selfgenerating source of nitrogen, has been proved beyond doubtviz. Legume-Rhizobium symbiosis and blue green algal ‘fertilizer’ for rice. The extent to which the free living, N-fixing, aerobic, heterotropicAzotobacter chroococcum could replace the application of nitrogenous fertilizer to maize was investigatedin vivo. Total nitrogen uptake (kg ha−1) by maize after inoculation with Azotobacter combined with moderate applications of nitrogen fertilizer and farmyard manure was influenced significantly and resulted in a higher nitrogen concentration in grain and stover along with a higher yield.
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  • 49
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    Plant and soil 69 (1982), S. 391-399 
    ISSN: 1573-5036
    Keywords: Associative nitrogen fixation ; Inoculation ; Nitrogen fixation ; Root exudate ; Soil bacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Organic components leaked fromSorghum bicolor seedlings (‘root exudates’) were examined by recovering14C labelled compounds from root solutions of seedlings inoculated withAzospirillum brasilense, Azotobacter vinelandii orKlebsiella pneumoniae nif-. Up to 3.5% of the total14C recovered from shoots, roots, and nutrient solutions was found in the root solutions. Inoculation with Azospirillum and Azotobacter increased the amounts of14C and decreased the amounts of carbohydrates in the root solutions. When sucrose was added as a carbon source for the bacteria, the increase of14C in the solutions did not occur. Quantities of14C found in the root solutions were proportional to amounts of mineral nitrogen supplied to the plants. Bacterial growth also was proportional to nitrogen levels. When sorghum plants were grown in soil and labelled with14CO2, about 15% of the total14C recovered within 48 hours exposure was found in soil leachates.
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  • 50
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    Plant and soil 100 (1987), S. 157-169 
    ISSN: 1573-5036
    Keywords: Legume ; Nitrogen fixation ; Nodule ; Translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen (N2) fixed by Rhizobium bacteroids in the legume nodule is excreted as ammonia to the surrounding host cell where it is efficiently assimilated into the amide group of glutamine. Generally glutamine is a minor exported solute of nitrogen, being further metabolised to asparagine in temperate species and to the ureides, allantoin and allantoic acid in tropical species. These solutes serve as the principal translocated forms of nitrogen in xylem. Compartmentalisation of the pathways of nitrogen metabolism and the role of ammonia in regulation of their activity is examined in nodules of both asparagine-forming (Lupinus albus L.) and ureide-forming (Vigna unguiculata L. Walp) symbioses.
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  • 51
    ISSN: 1573-5036
    Keywords: Isotope techniques ; Nitrogen-15 ; Nitrogen fixation ; Nitrogen utilization ; Phaseolus vulgaris ; Rhizobium ; Varietal comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Differences in N2-fixation byPhaseolus vulgaris bean cultivars were successfully evaluated in the field using15N isotope dilution technique with a non-fixing test crop of a different species (wheat). The Phaseolus cultivars could have been similarly ranked for N2-fixation capacity from either seed yield or total nitrogen yield, but the isotope method provided a direct measure of N2-fixation and made it possible to estimate the proportion of fixed to total nitrogen in the crop and in plant parts. Amounts of nitrogen fixed varied between 24.59 kg N/ha for the 60-day cultivar Goiano precoce to 64.91 kg N/ha for the 90-day cultivar Carioca. The per cent of plant nitrogen due to fixation was 57–68% for the 90-day cultivars and 37% for Goiano precoce (60-day cultivar). Fertilizer utilization was 17–30% of a 20 kg N/ha fertilizer application. 100 kg N/ha fertilizer application decreased N2-fixation without suppressing it totally. Differences in yield between the highest yielding (Carioca) and the lowest (Moruna) 90-day cultivars were also due apparently to varietal differences in efficiency of conversion of nitrogen to economic matteri.e. seed, as well as to differences in capacity of genotypes for N2-fixation.
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  • 52
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    Plant and soil 68 (1982), S. 217-222 
    ISSN: 1573-5036
    Keywords: Nitrogen fixation ; Oryza sativa ; Phragmites communis ; Reed ; Rhizosphere ; Rice ; Roots ; Soil temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relation of nitrogenase activity (ethylene evolution) to soil temperature or incubation temperature of roots was determined on two genera of swamp plants, namely rice (Oryza sativa) cultivated in tropical climate and reed (Phragmites communis) grown in temperate regions. For both intact rice plants and excised rice roots the optimum temperature was 35°C. On excised roots nitrogenase activity responded more sensitivity to changes in temperature. In contrast to intact rice plants no ethylene evolution occurred on excised roots at 17 and 44°C. On reed roots temperature optimum was between 26 and 30°C which is clearly lower than on rice (35°C). The temperature range in which nitrogen fixation occurred was, however, similar to that of rice, although on a lower level. The results suggest a higher potential of the tropics for associative N2 fixation, while in cooler climates the lower temperatures appear to be a major limiting factor.
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  • 53
    ISSN: 1440-1703
    Keywords: Acetylene reduction ; Antarctica ; Cyanobacteria ; Moss community ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen fixation by cyanobacteria in a moss community on East Ongul Island (69°00'S 39°35'E), Antarctica was investigated using the acetylene reduction method. The mean acetylene reduction rate at 10°C and 200 μE·m−2·s−1 photosynthetically active radiation was 7.12 nmol C2H4 per square centimeter of moss community per hour. The effects of temperature, radiation, desiccation and rehydration on the acetylene reduction rates were examined. A simple predictive model was constructed in order to estimate the amount of nitrogen fixed in the field. Using this model, the daily amount of nitrogen fixation was calculated from microclimatic data (temperature and radiation) measured in the experimental field at Syowa Station on East Ongul Island between 1983 and 1984. The cumulative amount of nitrogen fixation in the growing season during this period was estimated to be 329 mg N per square meter of moss community. It is suggested that nitrogen fixation by cyanobacteria in the moss community is important as a nitrogen source for the community growth on East Ongul Island.
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  • 54
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Lucerne ; Medicago sativa ; 15N methodology ; Nitrogen fixation ; Quantitative estimation ; Seasonal pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Lucerne is an important forage legume in the south and south-east of Sweden on well-drained soils. However, data is lacking on the apparent amount of nitrogen derived through N2 fixation by field-grown lucerne. This report provides basic information on the subject. The experiment was performed in a lucerne ley grown 40 km north of Uppsala. The input of nitrogen through fixation to the above-ground plant material of an established lucerne (Medicago sativa L.) ley was estimate by15N methodology during two successive years. The amount of fixed N was 242 kg N ha−1 in 1982 and 319 kg N ha−1 in 1983. The proportion of N derived from the atmosphere (%Ndfa) was 70% and 80% for the two years respectively. The first harvest in both years contained a lower proportion fixed N. Both N2 fixation and dry matter production were enhanced during the second year, particularly in the first harvest. The Ndfa was 61% in the first harvest in 1982, compared to 72% Ndfa during the same period in 1983. This demonstrates the strong influence of environment on both dry matter production and N2 fixation capacity of the lucerne. In addition anin situ acetylene reduction assay was used in 1982 to measure the seasonal distribution of the N2 fixation and in 1983 to study the effect of soil moisture on the N2 fixation process. The seasonal pattern showed great dependence on physiological development and harvest pattern of the lucerne ley. The maximum rate of N2 fixation occurred at the bud or early flower stage of growth and was followed by a rapid decline as flowering proceeded. After harvest the nitrogenase activity markedly decreased and remained low during at least two weeks until regrowth of new shoots began. Irrigation doubled the nitrogenase activity of the lucerne in late summer 1983, when soil moisture content in the top soil was near wilting point. No changes in nitrogenase activity did occur in response to watering earlier during the summer, when the soil matric potential was around −0.30 MPa.
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  • 55
    ISSN: 1573-5036
    Keywords: Foliar fertilization ; Fertilizer uptake efficiency ; Late fertilization ; Nitrogen-15 ; Nitrogen fixation ; Nitrogen translocation ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field experiments were conducted to determine the effects of the amount, time and method of fertilizer N application on the efficiency of N uptake, N2 fixatio and yield of soybean. Soil and foliar fertilizer N, applied during the pod-filling stage were absorbed by plants with equal and high efficiency, compared to an appreciably lower utilization efficiency for N applied before seedling emergence. These results reveal that the soybean roots were active in N uptake during these late stages of growth. Nitrogen fertilization during pod-filling resulted in significant yield increases over the control treatment which received an early application of 20 Kg N/ha. Seed yield increases were, however, more pronounced than total dry matter yield, and virtually all of the late-applied N was translocated into the pods. Nitrogen fixation in soybean was not influenced by the application of 40 kg N/ha to plants as soil or foliar N during the pod-filling stage. However, 80 kg N/ha supplied during pod-filling as 40 kg soil plus 40 kg foliar N/ha significantly reduced the amount of N2 fixed. The results obtained in these studies suggest that inadequate N supply during pod-filling limited soybean yields, and that by the judicious application of fertilizer N during the late stages of growth, it was possible to enhance soybean yields without necessarily inhibiting N2 fixation.
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  • 56
    ISSN: 1573-5036
    Keywords: Azolla ; Blue green alga ; Evapo-transpiratio chamber ; Humidity ; Light condition ; Nitrogen fixation ; Plant environment ; Symbiotic system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The construction and application of a new type of growth chamber, in which different growth conditionsi.e.: temperature, humidity, pH, light intensity, light colour, change in nutrient composition and gas exchange can easily be controlled, are presented. The method has previously been applied to twoAzolla speciesviz. Azolla filiculoides, which is cold tolerant andAzolla pinnata (distinguished in Vietnam as the form Xanh), which is heat tolerant. In the growth chamber natural growth conditions of the Azolla —Anabaena azollae symbiotic association were imitated as much as possible. For testing the system, methods discussed earlier8,14 and some previously presented data, concerning photosynthetic activities, such as oxygen evolution and nitrogen fixation (acetylene reduction) of twoAzolla species39, were partially used. Biomass ofA. filiculoides was measured and reactions to its environment at conditions when grown in the field and in the growth chamber, were studied. Growth and photosynthesis measurements were performed under special light conditions and with whole plants grown under laboratory conditions. Anthocyanin synthesis was studied in relation with humidity. Anthocyanin spectra were analyzed by means of a spectrum-deconvolution method.
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  • 57
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    Plant and soil 100 (1987), S. 171-181 
    ISSN: 1573-5036
    Keywords: Co-evolution ; Gene pool ; Nitrogen fixation ; Pisum sativum L. ; Rhizobium leguminosarum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A number of examples is given demonstrating the co-existence of pea genotypes and their specific Rhizobium, strains isolated within the same region.R. leguminosarum strains compatible with the cultivated pea have a narrow symbiotic range and they are widely distributed in European soils. This is presumably due to the narrow genetic base of the cultivated pea and its wide-spread cultivation in European soils. Rhizobium strains capable of nodulating a primitive pea line from Afghanistan were only found in soils of the Middle East and Central Asia. A more restricted distribution of specific Rhizobium strains was found for fulvum peas from Israel. Rhizobium strains effective with the fulvum pea were found in Israeli soils. A good example of co-evolution due to geographical isolation was found in south Turkey. Here a pea line was found which can form an effective symbiosis with local Rhizobium strains but not with strains from other parts of Turkey.
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  • 58
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    Plant and soil 100 (1987), S. 183-212 
    ISSN: 1573-5036
    Keywords: Anabaena azollae ; Azolla ; Desiccation ; Macrosporocarps ; Microsporocarps ; Nitrogen fixation ; Sexual reproduction ; Survival Azolla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The survival of Azolla was studied in an artificial system which simulated the soil/water interface and the desiccation of soil during a fallow period in lowland rice culture. Tests with non-sporulating and sporulating Azolla fronds showed that Azolla only survives with sporulated fronds. At their reappearance the Azolla fronds already harboured the Anabaena endophyte. A detailed light microscopic and transmission electron microscopic study of macro- and micros-porocarp formation and development revealed that the endophyte is transmitted by the macrosporocarps and not by the microsporocarps. The Anabaena cells within the macrosporocarps are found just below the indusium cap. These cells are not nitrogen-fixing akinetes. The free-living Anabaena cells at the stem apex and below the overarching developing leaves do not bear heterocysts and accordingly are non nitrogen-fixing. During the development of the leaf the Anabaena enters the leaf cavity, but later the pore of this, cavity closes and the imprisoned cyanobacteria are lysed before the leaf decays. As the Azolla leaves age a nitrogen-fixing capability is successively built up concomittantly with the production of heterocysts. Heterocyst frequencies of 40–50% can be found inAnabaena azollae. Usually a gradient of nitrogen-fixing capacity occurs along the Azolla rhizome with two distinct peaks at leaf number 7/8 and at leaf number 13/14 from the apex.
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  • 59
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    Plant and soil 98 (1987), S. 265-274 
    ISSN: 1573-5036
    Keywords: Alfalfa ; Birdsfoot trefoil ; Bromegrass ; Nitrogen fixation ; Nitrogen transfer ; Orchardgrass ; Red clover ; Red fescue ; Tall fescue ; Timothy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three legume species (alfalfa, red clover, and birdsfoot trefoil) in combination with five grass species (timothy, bromegrass, red fescue, tall fescue, and orchardgrass) were used to study N transfer in mixtures, using the 15N dilution technique. The advantage of grass-legume mixtures was apparent. Total herbage and protein yields of grasses in mixtures were higher than those alone, especially at the later cuts. This benefit of mixed cropping is mainly due to N transfer from legumes to associated grasses. N2-fixation and N transfer by alfalfa rated highest, red clover intermediate, and birdsfoot trefoil lowest. The importance of each pathway of N transfer from legumes appeared to differ between species. Alfalfa and red clover excreted more N than trefoil, while the latter contributed more N from decomposition of dead nodule and root tissue. The greatest advantage from a grass-legume mixture, with respect to the utilization of N released from the legume, varied with early maturing tall fescue (Kentucky 31), orchardgrass (Juno), and bromegrass (Tempo), to intermediate timothy (Climax), and least with late maturing red fescue (Carlawn).
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  • 60
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    Plant and soil 98 (1987), S. 425-428 
    ISSN: 1573-5036
    Keywords: Diazotrophs ; Ectomycorrhizae ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogenase activity, measured by acetylene reduction, was detected on nursery-grown, surface-sterilized ectomycorrhizae of Douglas-fir, formed withLaccaria laccata, Hebeloma crustuliniforme, Rhizopogon vinicolor, andThelephora sp. Detached mycorrhizae were incubated in nitrogen-free liquid medium under microaerophilic conditions. Nitrogenase activity was attributed toClostridium spp. andAzospirillum spp.
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  • 61
    ISSN: 1573-5036
    Keywords: Cajanus cajan ; Maturity groups ; Nitrogenase activity ; Nitrogen fixation ; Nitrogen uptake ; Nodulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The seasonal patterns of nodulation, acetylene reduction, nitrogen uptake and nitrogen fixation were studies for 11 pigeonpea cultivars belonging to different maturity groups grown on an Alfisol at ICRISAT Center, Patancheru, India. In all cultivars the nodule number and mass increased to a maximum around 60–80 days after sowing and then declined. The nodule number and mass of medium- and late-maturing cultivars was greater than that of early-maturing cultivars. The nitrogenase activity per plant increased to 60 days after sowing and declined thereafter, with little activity at 100 days when the crop was flowering. At later stages of plant growth nodules formed down to 90 cm below the soil surface but those at greater depth appeared less active than those near the surface. All the 11 cultivars continued to accumulate dry matter until 140 days, with most biomass production by the late-maturing cultivars (up to 11 t ha−1) and least by the early-maturing determinate cultivars (4 t ha−1). Total nitrogen uptake ranged from 69 to 134 kg ha−1. Nitrogen fixation by pigeonpea was estimated as the difference in total nitrogen uptake between pigeonpea and sorghum and could amount to 69 kg N ha−1 per season, or half the total nitrogen uptake. Fixation by pigeonpea increased with crop duration, but there were differences within each maturity group. The limitations of the methods used for estimating N2 fixation by pigeonpea are discussed.
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  • 62
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    Plant and soil 99 (1987), S. 285-290 
    ISSN: 1573-5036
    Keywords: Alder ; Actinomyces ; Nodulation ; Nitrogen fixation ; Purplish soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The alder has a perennial nodule cluster. The nodule amount on the roots increases with tree age. The N2-fixing activity of nodules decreases with nodule age. Purple coloured soils with various soil pHs and CaCO3 contents are, in the main, the ones which influence nodulation and N2-fixing. Higher N2-fixing capacity existed in the neutral and low calcium soils. High calcium soils and acid soils can restrain nodulation and the N2-fixing rate significantly. On the slope, where calcarous light loams are found, the annual nitrogen fixation capacity of alder and cypress mixed plantations, less than 10 years old, is 16 or 17 kg/ha yr, but in the valley, a pure alder plantation can reach 40 kg/ha yr.
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  • 63
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    Plant and soil 99 (1987), S. 435-439 
    ISSN: 1573-5036
    Keywords: Cowpea ; Effective nodulation ; Nitrogen fixation ; Nodule growth ; Plant age ; Rhizobium strain ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Rhizobium strains CIAT 301, CIAT 79 and SLM 602 were tested and found effective in the nodulation and nitrogen fixation of cowpea cv. MI-35 (Vigna unguiculata (L.) Walp) plants in growth chamber experiments. Fresh weight of nodules increased with plant age initially and stabilized in 20–30 days from planting, followed by a secondary flush of nodule growth after 30 days. Apparent nitrogen fixation per gram nodule fresh weight reached a maximum in 20–30 days after planting and then decreased, even though a flush of new nodules was produced.
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