Acetylene-induced decline in acetylene reduction by nodulated roots of alfalfa

1989 ◽  
Vol 67 (2) ◽  
pp. 360-364 ◽  
Author(s):  
F. D. H. Macdowall ◽  
G. T. Kristjansson
Keyword(s):  
Growth Temperature ◽  
Acetylene Reduction ◽  
Respiratory Activity ◽  
Rhizobium Meliloti ◽  
Continuous Treatment ◽  
Short Term ◽  
Medicago Sativa L ◽  
Reducing Activity ◽  
Acetylene Reducing Activity ◽  
Lower Temperature

Seedlings of three cultivars of alfalfa (Medicago sativa L.) were nodulated with two strains of rhizobia (Rhizobium meliloti) and grown with zero N nutrients at 25:20 °C for 6 weeks followed by growth at 10:7 °C for 2 weeks. Acetylene-reducing activity (ARA) was retarded by 10% acetylene to an extent dependent on time, cultivar, strain, and growth temperature. In the usual short term assay for nitrogenase by ARA, the inhibition was not sufficient to explain decreased apparent efficiency of nitrogenase in plants moved to the lower temperature. Inhibition of ARA was associated with correspondingly decreased respiration in cv. Drylander, but in cv. Apollo respiration was not affected. The differential loss of ARA relative to respiratory activity in a day of continuous treatment with 10% acetylene was very distinct and requires an explanation other than altered nodule resistance to diffusion of oxygen.

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.

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.

scholarly journals Nitrogenase of Klebsiella pneumoniae. Inhibition of acetylene reduction by magnesium ion explained by the formation of an inactive dimagnesium–adenosine triphosphate complex

1974 ◽  
Vol 139 (1) ◽  
pp. 211-214 ◽  
Author(s):  
Roger N. F. Thorneley ◽  
Keith R. Willison
Keyword(s):  
Klebsiella Pneumoniae ◽  
Adenosine Triphosphate ◽  
Acetylene Reduction ◽  
Inhibitory Effect ◽  
Magnesium Ion ◽  
Active Substrate ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Acetylene-reducing activity of purified nitrogenase from Klebsiella pneumoniae was studied over a range of ATP and Mg2+ concentrations at 15°C, pH7.8. Inhibition at Mg2+ concentrations of 2.5–30mm was due to the formation of the inactive complex, Mg2ATP. At higher Mg2+ concentrations an additional inhibitory effect was observed. The results were consistent with a MgATP complex being the active substrate with an apparent Km(MgATP)=0.4mm.

Factors affecting vesicle formation and acetylene reduction (nitrogenase activity) in Frankia sp. CpI1

1981 ◽  
Vol 27 (8) ◽  
pp. 815-823 ◽  
Author(s):  
John D. Tjepkema ◽  
William Ormerod ◽  
John G. Torrey
Keyword(s):  
Acetylene Reduction ◽  
Ethylenediaminetetraacetic Acid ◽  
Nitrogenase Activity ◽  
Carbon Sources ◽  
Vesicle Formation ◽  
Free Medium ◽  
Factors Affecting ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

Vesicle formation and acetylene reduction (nitrogenase activity) were observed when washed hyphae from cultures of Frankia sp. CpI1 were transferred to a nitrogen-free medium containing ethylenediaminetetraacetic acid and succinate. Succinate could be replaced by malate or fumarate, but not other carbon sources. Maximum acetylene reduction and vesicle numbers were observed at a pH of 6.0–6.5, at 25–30 °C, and at atmospheric [Formula: see text] or somewhat less (5–20 kPa). Addition of 1 mM NH4Cl almost completely inhibited vesicle formation and acetylene-reducing activity, but did not immediately inhibit such reducing activity by cultures with preexisting vesicles. Acetylene-reducing activity was never observed in the absence of vesicle formation.

ATP and acetylene-reducing activity of a sulfate-reducing bacterium

1977 ◽  
Vol 23 (5) ◽  
pp. 567-572 ◽  
Author(s):  
T. Sekiguchi ◽  
A. Noguchi ◽  
Y. Nosoh
Keyword(s):  
Energy Source ◽  
Sulfate Reduction ◽  
Acetylene Reduction ◽  
Adenine Nucleotides ◽  
Desulfovibrio Vulgaris ◽  
Atp Level ◽  
Sulfate Reducing ◽  
Reducing Activity ◽  
Acetylene Reducing Activity

A sulfate-reducing bacterium, a strain of Desulfovibrio vulgaris, when lactate or pyruvate was supplied as an electron and energy source, reduced acetylene only in the presence of sulfate. Acetylene reduction started after a lag of 1 h. H2 which acts as an electron and energy source for sulfate reduction was unable to reduce acetylene even in the presence of sulfate. It was suggested, from the measurements of the amounts of adenine nucleotides of the bacterium incubated under various conditions, that the bacterium is able to reduce acetylene at a high ATP level or a high ATP/ADP ratio.

Overexpression of the dctA gene in Rhizobium meliloti: effect on transport of C4 dicarboxylates and symbiotic nitrogen fixation

1992 ◽  
Vol 38 (6) ◽  
pp. 555-562 ◽  
Author(s):  
Vipin Rastogi ◽  
Monika Labes ◽  
Turlough Finan ◽  
Robert Watson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Symbiotic Nitrogen Fixation ◽  
Plasmid Stability ◽  
Rhizobium Meliloti ◽  
Mrna Synthesis ◽  
Dicarboxylate Transport ◽  
Fusion Strain ◽  
Tryptophan Operon ◽  
Specific Mrna

Symbiotic nitrogen fixation may be limited by the transport of C4 dicarboxylates into bacteroids in the nodule for use as a carbon and energy source. In an attempt to increase dicarboxylate transport, a plasmid was constructed in which the Rhizobium meliloti structural transport gene dctA was fused to a tryptophan operon promoter from Salmonella typhimurium, trpPO. This resulted in a functional dctA gene that was no longer under the control of the dctBD regulatory genes, but the recombinant plasmid was found to be unstable in R. meliloti. To stably integrate the trpPO-dctA fusion, it was recloned into pBR325 and recombined into the R. meliloti exo megaplasmid in the dctABD region. The resultant strain showed constitutive dctA-specific mRNA synthesis which was about 5-fold higher than that found in fully induced wild-type cells. Uptake assays showed that [14C]succinate transport by the trpPO-dctA fusion strain was constitutive, and the transport rate was the same as that of induced control cells. Acetylene reduction assays indicated a significantly higher rate of nitrogen fixation in plants inoculated with the trpPO-dctA fusion strain compared with the control. Despite this apparent increase, the plants had the same top dry weights as those inoculated with control cells. Key words: acetylene reduction, genetic engineering, nodule, plasmid stability, promoter.

scholarly journals Effect of Growth Temperature on Aster Flower Development

HortScience ◽  
2000 ◽  
Vol 35 (1) ◽  
pp. 28-29 ◽  
Author(s):  
M. Oren-Shamir ◽  
L. Shaked-Sachray ◽  
A. Nissim-Levi ◽  
D. Weiss
Keyword(s):  
Growth Temperature ◽  
Flower Development ◽  
Flower Longevity ◽  
Dramatic Effect ◽  
Controlled Conditions ◽  
Higher Temperature ◽  
Temperature Controlled ◽  
Lower Temperature

Little is known about the effect of growth temperature on Aster (Compositae, Asteraceae) flower development. In this study, we report on this effect for two aster lines, `Suntana' and `Sungal'. Growth temperature had a dramatic effect on the duration of flower development, ranging from 22 days for plants growing at 29 °C up to 32 days for plants grown at 17 °C. Flower longevity was ≈40% shorter under the higher temperature for both lines. Growth temperature also affected flowerhead form: `Suntana' flowerhead diameter was 20% larger at 17 °C than at 29 °C. The number of `Sungal' florets per flowerhead was four times greater at the lower temperature. Shading (30%) under temperature-controlled conditions had no effect on any of the parameters measured. For plants grown outdoors, our results suggest that shading plants may increase quality by reducing the growth temperature.

Sign in / Sign up

Export Citation Format

Share Document