scholarly journals Endorhizal and Exorhizal Acetylene-reducing Activity in a Grass (Spartina alterniflora Loisel.)-Diazotroph Association

1980 ◽  
Vol 66 (2) ◽  
pp. 276-280 ◽  
Author(s):  
C. David Boyle ◽  
David G. Patriquin
Keyword(s):  
Spartina Alterniflora ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Nitrogen fixation (acetylene reduction) by Klebsiella pneumoniae in association with 'Park' Kentucky bluegrass (Poa pratensis L.)

1981 ◽  
Vol 27 (1) ◽  
pp. 52-56 ◽  
Author(s):  
L. V. Wood ◽  
R. V. Klucas ◽  
R. C. Shearman
Keyword(s):  
Nitrogen Fixation ◽  
Klebsiella Pneumoniae ◽  
Ethylene Production ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Poa Pratensis ◽  
Kentucky Bluegrass ◽  
Surface Sterilization ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Turfs of 'Park' Kentucky bluegrass reestablished in the greenhouse and inoculated with Klebsiella pneumoniae (W6) showed significantly increased nitrogen fixation (acetylene reduction) compared with control turfs. Mean ethylene production rates per pot were 368 nmol h−1 for K. pneumoniae treated turfs, 55 nmol h−1 for heat-killed K. pneumoniae treated turfs, and 44 nmol h−1 for untreated turfs. Calculated lag periods before activity was observed were generally very short (less than 1 h).When 'Park' Kentucky bluegrass was grown from seed on soil-less medium of Turface, a fired aggregate clay, inoculation with K. pneumoniae (W6) resulted in 9 of 11 turfs showing nitrogenase activity (mean ethylene producion rate per pot was 195 nmol h−1). Only 3 of 11 turfs treated with heat-killed K. pneumoniae showed any activity and their mean rate of ethylene production (40 nmol h−1 per pot) was significantly lower than that for turfs treated with K. pneumoniae.Using the 'Park'–Turface soil-less model system it was shown that acetylene reducing activity was (i) root associated, (ii) generally highest at a depth of 1–4 cm below the surface, (iii) enhanced by washing excised roots, and (iv) inhibited by surface sterilization of excised roots. Klebsiella pneumoniae was recovered from Turface and roots showing acetylene reducing activity.

Kinetics of first-cutting regrowth of alfalfa plants and nitrogenase activity in a controlled environment with and without added nitrate

1983 ◽  
Vol 61 (9) ◽  
pp. 2405-2409 ◽  
Author(s):  
F. D. H. Macdowall
Keyword(s):  
Dry Matter ◽  
Rhizobium Meliloti ◽  
Nitrogenase Activity ◽  
Radical Change ◽  
N Nutrition ◽  
Meliloti Strain ◽  
Medicago Sativa L ◽  
Reducing Activity ◽  
Acetylene Reducing Activity ◽  
Kinetics Of

Seedlings of Medicago sativa L. cv. Algonquin were grown in vermiculite and nodulated by Rhizobium meliloti strain 102F70 at two lower levels of N, until flowering when the tops were cut off to leave about 10% shoot stubble. Residual shoot dry matter immediately resumed first-order growth and maintained it throughout regrowth to second flowering. The rate constants of shoot regrowth were 34% lower (at 15 mM NO3−), 25% lower (at 1.5 mM NO3− symbiotically), or 220% higher (at zero NO3− symbiotically) than the values for 1 to 4-week-old seedlings, which indicated a radical change in physiology. Root dry matter resumed exponential growth after a 7-day recession and its recovery and yields were independent of N nutrition. The most pronounced minima occurred in the acetylene-reducing activity of nitrogenase, the kinetics of which paralleled root dry matter except that its redevelopment stopped after two-thirds of the regrowth time. The rate coefficient for the redevelopment of nitrogenase activity equalled that for its development during the seedling stage, which suggested unchanged limitations on that process until its redevelopment stopped.

Acetylene-reducing activity of detached root nodules ofMyrica faya ait

1974 ◽  
Vol 41 (3) ◽  
pp. 521-526 ◽  
Author(s):  
C. Miguel ◽  
C. Rodriguez-Barrueco
Keyword(s):  
Root Nodules ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

scholarly journals The Basis of Ammonium Release in nifLMutants of Azotobacter vinelandii

1999 ◽  
Vol 181 (23) ◽  
pp. 7356-7362 ◽  
Author(s):  
Brett Brewin ◽  
Paul Woodley ◽  
Martin Drummond
Keyword(s):  
Azotobacter Vinelandii ◽  
Transcriptional Level ◽  
Uptake System ◽  
Wild Type ◽  
Two Component System ◽  
Two Component ◽  
In The Wild ◽  
Reducing Activity ◽  
State Growth ◽  
Acetylene Reducing Activity

ABSTRACT In Azotobacter vinelandii, nitrogen fixation is regulated at the transcriptional level by an unusual two-component system encoded by nifLA. Certain mutations innifL result in the bacterium releasing large quantities of ammonium into the medium, and earlier work suggested that this occurs by a mechanism that does not involve NifA, the activator ofnif gene transcription. We have investigated a number of possible alternative mechanisms and find no evidence for their involvement in ammonium release. Enhancement of NifA-mediated transcription, on the other hand, by either elimination ofnifL or overexpression of nifA, resulted in ammonium release, correlating with enhanced levels of nifHmRNA, raised levels of nitrogenase and acetylene-reducing activity, and increased concentrations of intracellular ammonium. Up to 35 mM ammonium can accumulate in the medium. Where measured, intracellular levels exceeded extracellular levels, indicating that rather than being actively transported, ammonium is lost from the cell passively, possibly by reversal of an NH4 + uptake system. The data also indicate that in the wild type the bulk of NifA is inactivated by NifL during steady-state growth on dinitrogen.

New incubation device forin situ measurement of acetylene-reducing activity in ricefields

1989 ◽  
Vol 1 (3) ◽  
pp. 195-200 ◽  
Author(s):  
Antonio Quesada ◽  
Eva Sanchez Maeso ◽  
Eduardo Fernandez Valiente
Keyword(s):  
Reducing Activity ◽  
Acetylene Reducing Activity

Acetylene reducing activity at a tropical seagrass bed in Papua New Guinea

1992 ◽  
Vol 48 (4) ◽  
pp. 377-384 ◽  
Author(s):  
Hitoshi Iizumi
Keyword(s):  
Papua New Guinea ◽  
New Guinea ◽  
Seagrass Bed ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Use of spermosphere model for the screening of wheat cultivars and N2-fixing bacteria for N2 fixation

1986 ◽  
Vol 32 (4) ◽  
pp. 285-288 ◽  
Author(s):  
Devender K. Jain ◽  
R. J. Rennie
Keyword(s):  
Yeast Extract ◽  
N2 Fixation ◽  
Azospirillum Brasilense ◽  
Incubation Temperature ◽  
Wheat Cultivars ◽  
Wheat Roots ◽  
Naoh Solution ◽  
Reducing Activity ◽  
Acetylene Reducing Activity ◽  
Very High

The spermosphere model showed very high seedling-to-seedling variation in the ability to induce acetylene-reducing activity in bacteria associated with wheat roots. Several seedlings failed to induce nitrogenase in N2-flxing strains of Bacillus and Azospirillum brasilense. Increasing the concentration of yeast extract or the inoculum density, adding NaOH solution in the side arm of Pankhurst tubes to absorb CO2, and vernalizing the seeds did not increase the percentage of nitrogenase-positive tubes and did not decrease variation in acetylene-reducing activity. Increasing the incubation temperature from 25 to 27 °C induced nitrogenase in Bacillus, but not in Azospirillum strains; at 30 °C nitrogenase was also induced in Azospirillum strains. It appears that the spermosphere model is not a practical technique for screening nitrogenase induction by wheat, unless the use of genetic lines of unimpeachable uniformity can provide control of variability.

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