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  • 1
    Electronic Resource
    Electronic Resource
    Effect of high root temperature on Bradyrhizobium-peanut symbiosis (1992)
    Springer
    Plant and soil 143 (1992), S. 275-282 
    Details
    ISSN: 1573-5036
    Keywords: Arachis ; Bradyrhizobium ; heat-shock proteins ; nitrogen fixation ; peanut ; root temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three strains of Bradyrhizobium, 280A, 2209A and 32H1, that nodulated peanuts (Arachis hypogaea L.), were tested for their ability to grow and survive at elevated temperatures of up to 42°C in laboratory culture. Strain 32H1 was unable to grow at 37°C and was more sensitive to elevated temperatures than the other two strains. All three produced heat-shock proteins of molecular weights 17 kDa and 18 kDa. Two greenhouse experiments were conducted to determine the effect of high root temperature on nodulation, growth and nitrogen fixation of peanut. Two peanut varieties (Virginia cv NC7 and Spanish cv Pronto) were inoculated and exposed to root temperatures of 30°, 37° and 40°C. Nodulation and nitrogen fixation were strongly affected by root temperature but there was no variety × temperature interaction. At a constant 40°C root temperature no nodules were formed. Nodules were formed when roots were exposed to this temperature with diurnal cycling but no nitrogen fixation occurred. Highest plant dry weight, shoot nitrogen content and total nitrogen were observed at a constant root temperature of 30°C. Increasing root temperature to 37°C reduced average nitrogen content by 37% and total nitrogen by 49% but did not reduce nodulation. The symbiotic performance of the strains corresponded to their abilities to grow and survive at high temperature in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007883
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  • 2
    Electronic Resource
    Electronic Resource
    Partitioning of biologically fixed nitrogen in cowpea during pod development (1989)
    Springer
    Plant and soil 116 (1989), S. 129-131 
    Details
    ISSN: 1573-5036
    Keywords: 15N ; nitrogen fixation ; nitrogen partitioning ; translocationVigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two days after exposure of roots to15N labeled N2, partitioning of biologically fixed N into leaves, stems, peduncles, pods, roots and nodules was measured in the early pod development stage of cowpea (Vigna unguiculata (L.). The experimental objective was to determine the quantity of biologically fixed N that is incorporated into vegetative tissue before being mobilized to pods. For the three varieties of cowpea included in the experiment a maximum of 50% of the N, biologically fixed two days earlier, was contained in the pods. The remaining N was distributed throughout the vegetative portion of the plant with at least 30% in stems and leaves which indicates that much of the newly fixed N must cycle through a N pool in these tissues before reaching the pods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02327269
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  • 3
    Electronic Resource
    Electronic Resource
    Nodulation and N2 fixation of guar at high root temperature (1990)
    Springer
    Plant and soil 126 (1990), S. 209-213 
    Details
    ISSN: 1573-5036
    Keywords: Cyamopsis ; guar ; heat ; nitrogen fixation ; rhizobia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Guar (Cyamopsis tetregonoloba (L.) may be grown when soil temperatures are potentially high enough at the time of planting to inhibit nodulation and N2 fixation. An experiment was conducted using controlled conditions to determine the influence of high root temperature on growth and N2 fixation of guar. The experiment included two strains of rhizobia, two varieties of guar, two mineral N treatments, and root temperatures of 34, 37, and 40°C. Plants were grown for 44 days. The root temperature of 40°C reduced N fixation by at least 80% and nodule weight by more than 50%. Significant interactions occurred between most factors in influencing nodulation, N2 fixation and dry matter production. Guar, nodulated by rhizobial strain GAR022-1 and fully dependent on N2 fixation or provided with starter mineral N (25 mg pot−1), was not influenced by the root temperature of 37°C as compared to 34°C. Nodulation and N2 fixation by strain 32H1 was reduced by at least 40% when no starter mineral N was provided and the root temperature was 37°C. Providing starter mineral N to one variety of guar doubled the quantity of N2 fixed by strain 32H1 at both 34 and 37°C but N2 fixation was lower at the higher root temperature. It appears that root temperatures between 37° and 40°C bracketed the critical root temperature for N2 fixation by nodulated guar and that the critical root temperature for guar dependent on mineral N was above 40°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00012824
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  • 4
    Electronic Resource
    Electronic Resource
    Number of Rhizobia and delayed inoculation influence nodulation of clovers (1994)
    Springer
    Plant and soil 158 (1994), S. 135-139 
    Details
    ISSN: 1573-5036
    Keywords: clover ; inoculation ; nitrogen fixation ; nodulation ; rhizobia ; Trifolium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The relationship between numbers of rhizobia and nodulation response of legumes is of considerable practical importance. Experiments were done under controlled conditions to determine the influence of numbers of Rhizobium leguminosarum biovar. trifolii on nodulation of arrowleaf clover (Trifolium vesiculosum Savi.) and crimson clover (T. incarnatum L.). Numbers of rhizobia in excess of 1000 per seed did not substantially increase earliness of nodulation or total number of nodules formed on the taproot. Nodules, however, were formed nearer the top of the taproot as numbers of rhizobia increased to 100,000 per seed. Delayed inoculation experiments indicated that nodulation sites for these clovers only remained susceptible to infection for less than 1 day. Delaying inoculation for 4 days resulted in only a 1 to 2 day delay in nodulation for arrowleaf and crimson clovers respectively and no delay for subterranean clover (T. subterraneum L.). Apparently, larger seedlings nodulated faster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00007926
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  • 5
    Electronic Resource
    Electronic Resource
    Distribution of 15N from ammonium fertilizer in field grown Acacia (1993)
    Springer
    Plant and soil 151 (1993), S. 147-150 
    Details
    ISSN: 1573-5036
    Keywords: Acacia ; isotope dilution ; nitrogen fixation ; N15 ; nitrogen partitioning ; tree
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract An experiment was conducted in the field to determine the partitioning of 15N from ammonium sulfate fertilizer in two-year old trees of Acacia mangium and Acacia auriculiformis. For both species, most of the 15N excess was partitioned into woody tissue, green material and root biomass present at the beginning of the experiment. Approximately one third of the 15N excess was contained in leaves that developed during the 60 days of the experiment. The concentration of 15N excess in the newly developed leaves indicated that more than 90% of the N came from a source other than the fertilizer. Based on the large quantity of N applied in the fertilizer and the inherently infertile soil, it appears that much of the N contained in the newly developed leaves came from N remobilized from other tree parts. ei]{gnR O D}{fnDixon}
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010796
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  • 6
    Electronic Resource
    Electronic Resource
    Distribution of fixed-N and nitrate-N in cowpea during pod development (1993)
    Springer
    Plant and soil 155-156 (1993), S. 353-354 
    Details
    ISSN: 1573-5036
    Keywords: cowpea ; nitrogen fixation ; nitrate ; partitioning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract If the quality and quantity of yields from cowpea (Vigna unguiculata [L.] Walp.) are to be maximised, a complete understanding of the N nutrition of the plant must be achieved. The N requirement for developing pods of this species may come from mobilization of N in vegetative tissue, biological N fixation and uptake of N from soil. In this study, the fate of a pulse of fixed 15N2 or of 15NO3-given to different cowpea plants during pod development was determined. The plants were grown in vermiculite in plastic pots that were able to be sealed with silicone adhesive and equipped with a rubber septum so that 15N2 gas could be injected into the air space above the vermiculite, and gas losses would be eliminated. Nineteen days after injection of 15N2 the pods, leaves, nodules and roots contained 65%, 15%, 9%, and 4%, respectively of the quantity of 15N2 fixed. When 15NO3-15N was taken up by other plants during this period, these plant parts contained 40%, 26%, 3% and 19%, respectively, of the total plant 15N. The percentage 15N in roots was greater, and that of 15N in nodules was lower, when 15NO3-15N was applied than when 15N2 was utilised by plants. These results indicate that, while a high percentage of fixed-N or NO3-N given to cowpea plants moved to the developing pods, other sinks were competing for this newly-aquired N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025055
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  • 7
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    On the formation and confinement of dense clouds in QSOs and active galactic nuclei (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A model for the formation and confinement of dense (at least about 1 billion per cu cm) clouds in QSOs and active galactic nuclei is presented wherein thermal instabilities behind radiative shocks cause the collapse of regions where the preshock density is enhanced over that of the surrounding medium. Such shocks (of total energy around 10 to the 51st ergs) are likely to occur if the frequent optical outbursts observed in many of these objects are accompanied by mass ejections of comparable energy. It is found that clouds quite similar to those thought to exist in QSOs etc. can be created in this manner at radii of the order of 10 to the 17th cm. The clouds can be subsequently accelerated to observed bulk velocities by either radiation pressure or a collision with a much stronger (total energy around 10 to the 53 ergs) shock. Alternatively, their high observed velocities could be caused by gravitational infall or rotation. The mass production required at inner radii by the outflow models can be supplied through a mechanism previously discussed by Shields (1977).
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 227
    Format: text
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  • 8
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    Consequences of narrow cyclotron emission from Hercules X-1 (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Explanations of the line feature in the hard X-ray (58 keV) spectrum of the compact X-ray source Hercules X-1 are presented. The most important characteristic of the emission (interpreted as a cyclotron emission from a strong magnetic field, i.e., B greater than one trillion Gauss) is that the FWHM is less than 12 keV, with a total observed luminosity in the line of approximately 1% of the total X-ray luminosity. If the source region is only at the magnetic poles of a neutron star, the electrons are confined to a path nearly parallel to the B-field lines, and the angle of emission will be narrow. Photon emission under such circumstances is also discussed; and it is suggested that photons can leave either through holes in the shell formed by the hard X-rays, or can escape through the shell itself. Attention is given to the accretion flow structure near the magnetopause, as a critical parameter of narrow line emission.
    Keywords: ASTROPHYSICS
    Type: Nature; vol2 274
    Format: text
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  • 9
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    Structure of the iron fluorescence line in X-ray binaries (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper presents an approximate solution to the iron K alpha line transfer problem in a stellar atmosphere illuminated by an external X-ray source as in a binary X-ray system. The emergent Comptonized line profile can independently yield information on the abundance of heavy elements in the primary atmosphere and on the solid angle subtended by the primary at the X-ray source.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 215
    Format: text
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  • 10
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    A new luminosity limit for spherical accretion onto compact X-ray sources (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Preheating of infalling gas by emergent X-rays can suppress accretion on to a compact X-ray source. For spherically symmetric accretion, the effect results in a new luminosity limit, orders of magnitude less than the Eddington limit, above which steady flow is impossible. The model may apply to the globular-cluster X-ray sources.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 208; Sept. 1
    Format: text
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