The temperature dependence of thallus nitrogenase activity in Peltigera canina

1975 ◽  
Vol 53 (6) ◽  
pp. 527-529 ◽  
Author(s):  
E. Maikawa ◽  
K. A. Kershaw
Keyword(s):  
Nitrogen Fixation ◽  
Temperature Dependence ◽  
Soil Nitrogen ◽  
Acetylene Reduction ◽  
Reduction Method ◽  
Nitrogenase Activity ◽  
Low Levels ◽  
Peltigera Canina

Comparative rates of nitrogen fixation in the lichen Peltigera canina from subarctic and temperate habitats have been examined using the acetylene reduction method. Maximum acetylene reduction at thallus saturation and with 20000 lx illumination takes place at 16 °C in subarctic material and at 21 °C in temperate material. This adaptation of nitrogenase activity to temperature in P. canina is discussed in relation to low levels of soil nitrogen in arctic systems.

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.

Nitrogen fixation and photosynthesis in high arctic forms of Nostoc commune

1994 ◽  
Vol 72 (7) ◽  
pp. 940-945 ◽  
Author(s):  
R. Lennihan ◽  
D. M. Chapin ◽  
L. G. Dickson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Terrestrial Ecosystems ◽  
Growing Season ◽  
High Arctic ◽  
Colony Morphology ◽  
Nostoc Commune ◽  
Devon Island ◽  
Low Levels ◽  
Temperature Optima

Nostoc commune, a colonial cyanobacterium, has been suggested as an important contributor of nitrogen to terrestrial ecosystems in the Canadian High Arctic, yet little is known about the ecophysiology of this organism in arctic environments. This study focused on the physiological performance of macroscopic colonies of N. commune found on Devon Island, N.W.T. The objectives were to examine the influence of temperature, colony morphology, and seasonal phenology on nitrogen fixation rates and the effects of light and temperature on photosynthesis. Maximum rates of acetylene reduction in N. commune (2119 nmol C2H4∙g−1∙h−1) were higher than those previously recorded for arctic N. commune but lower than values reported for temperate poulations. Depending on the time of the growing season, the temperature optimum for acetylene reduction varied from 15 °C to greater than 20 °C. Photosynthetic temperature optima did not occur below 20–25 °C (the highest temperatures measured). Light saturation of photosynthesis was reached at low levels of irradiance (100–150 μmol∙m−2∙s−1 PPFD). Acetylene reduction rates varied strongly with colony morphology. Thin, fragile, flattened colonies had higher rates than thicker, more resilient, flattened colonies or spherical colonies. Cold post-thaw temperatures appeared to delay the recovery of maximum nitrogen fixation rates for 2–3 weeks following the onset of the growing season. Compared with two other species of cyanobacteria present on Truelove Lowland (Gloeocapsa alpina and Gleotrichia sp.), N. commune had higher rates of nitrogen fixation. Key words: Nostoc commune, cyanobacteria, High Arctic, nitrogen fixation, photosynthesis.

Potential for nitrogen fixation in the rhizosphere and habitat of natural stands of the wild rice Zizania aquatica

1979 ◽  
Vol 57 (11) ◽  
pp. 1285-1291 ◽  
Author(s):  
M. T. Ogan
Keyword(s):  
Nitrogen Fixation ◽  
Water Column ◽  
Acetylene Reduction ◽  
Wild Rice ◽  
Heterotrophic Bacteria ◽  
Nitrogenase Activity ◽  
Early Summer ◽  
Zizania Aquatica ◽  
Natural Stands ◽  
Root Surfaces

The potential for nitrogen fixation in the rhizosphere and habitat of natural stands of Zizania aquatica (L) was studied by the acetylene reduction method. The data obtained suggested that this potential exists in the water column, the rhizosphere soil of the wild rice habitat, and on the root surfaces of the plants.In situ determination of rates of nitrogen fixation in the water column showed low but significant levels only in late spring – early summer and the rate was thought to be dependent on the presence of the blue-green algae Aphanizomenon. Laboratory experimental evidence showed that acetylene reduction by rhizosphere surface soil was attributable to Oscillatoria species while bacteria were more active in the subsurface soil and on the root surfaces. The bacteria-mediated nitrogenase activity was often preceded by a long lag period. The heterotrophic bacteria involved were enumerated, isolated, and characterised and they belong to the genera Azotobacter and Clostridium. Algal components of blooms occurring within the stands of Zizania at various times were identified.

Estimate of nitrogen fixation on leaf surfaces of forest species in Minnesota and Oregon

1979 ◽  
Vol 9 (4) ◽  
pp. 474-477 ◽  
Author(s):  
Edward Sucoff
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Reduction Method ◽  
Forest Species ◽  
Shrub Species ◽  
Nitrogen Economy ◽  
Upper Limits ◽  
Leaf Surfaces

Leafy branches from 52 tree or shrub species collected from Minnesota forests during July and August, 1976, and (or) May and September, 1977, were tested for their ability to fix nitrogen. Seven species were similarly sampled in western Oregon during November, 1976. Nitrogen fixation was assessed by the acetylene reduction method. Little, if any, acetylene reduction was detected on branches without epiphytes. The upper limits of possible nitrogen fixation on the leaf surfaces were below amounts important in the nitrogen economy of the stands.

Nitrogen Fixation (Acetylene Reduction) Associated with Sea Urchins (Strongylocentrotus droebachiensis) Feeding on Seaweeds and Eelgrass

1977 ◽  
Vol 34 (3) ◽  
pp. 416-420 ◽  
Author(s):  
M. L. Guerinot ◽  
W. Fong ◽  
D. G. Patriquin
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Sea Urchins ◽  
Nitrogenase Activity ◽  
Average Rate ◽  
Strongylocentrotus Droebachiensis ◽  
Molar Ratio ◽  
Laminaria Digitata ◽  
Bare Rock ◽  
Nitrogenase Activities

Sea urchins feeding in different macrophyte zones in St. Margaret's Bay, Nova Scotia, in November and December 1975 were examined for nitrogenase activity using the acetylene reduction technique. For sea urchins feeding on Laminaria digitata and L. longicruris, the average rate of acetylene reduction was equivalent to N2 fixation of 55 μg N2 per sea urchin per day assuming a 3:1 molar ratio of C2H2 reduction to N2 fixation. Lower nitrogenase activities were observed for sea urchins feeding on Agarum cribrosum and Zostera marina, and no nitrogenase activity was observed for sea urchins taken from bare rock substrate on which kelp had been absent for 4 yr. Samples of separated digestive tracts but not the degutted bodies of sea urchins exhibited nitrogenase activity, suggesting that the digestive tract is the site of nitrogen fixation in whole sea urchins.

Nitrogen fixation in forests of central Massachusetts

1979 ◽  
Vol 57 (1) ◽  
pp. 11-16 ◽  
Author(s):  
John Tjepkema
Keyword(s):  
Nitrogen Fixation ◽  
Tree Species ◽  
Acetylene Reduction ◽  
Time Course ◽  
Reduction Method ◽  
Old Fields ◽  
Soil Cores ◽  
Nitrogen Inputs ◽  
Woody Litter

The acetylene reduction method was used to measure nitrogen fixation in soil cores of 16 cm diameter and 16 cm depth that included A and B horizon soil, roots, and decaying litter. Forty-three combinations of location and associated tree species were sampled. The rate of nitrogen fixation for most soil cores was 1 g N ha−1 day−1 or less, which extrapolates to less than 0.2 kg N ha−1 year−1. The highest rates, with values of up to 23 g N ha−1 day−1, were observed in old fields being invaded by trees. The time course of acetylene reduction was usually linear for a 24-h period, most of the activity was in the upper 15 cm of soil, and the maximum rates were observed in midsummer. No significant nitrogen fixation was observed in preliminary measurements of decaying woody litter or of aerial surfaces of trees and rocks. It is suggested that nitrogen fixation is not a significant input of nitrogen for the forests studied. If so, there may be significant unrecognized nitrogen inputs to forests, such as dry absorption of ammonia from the atmosphere.

Seasonal and diurnal variation of nitrogenase activity (acetylene reduction) in barrel medic (Medicago truncatula Gaertn.) grown in pots

1978 ◽  
Vol 29 (5) ◽  
pp. 951 ◽  
Author(s):  
JJ Ruegg ◽  
AM Alston
Keyword(s):  
Nitrogen Fixation ◽  
Diurnal Variation ◽  
Medicago Truncatula ◽  
Acetylene Reduction ◽  
Time Course ◽  
Nitrogenase Activity ◽  
Seasonal Pattern ◽  
Molar Ratio ◽  
Multiple Use ◽  
Seasonal And Diurnal Variation

Seasonal and diurnal variation of nitrogenase activity in Medicago truncatula Gaertn. was measured by means of the acetylene reduction assay on plants grown in pots. In a glasshouse set at 20°C, the seasonal pattern of acetylene reduction (AR) activity was closely correlated with dry weight and photosynthetic area. Short-term fluctuations in AR activity were mainly associated with irradiance. Measurements made of the diurnal variation of AR activity showed that rates of AR at noon were 10–60% (average 33%) higher than the mean daily rates. Effects of defoliation and shading gave further evidence for the importance of light and recent photosynthate for nitrogen fixation in root nodules of legumes. Values for acetylene reduction integrated over time were highly correlated with the total amount of nitrogen in the plant. The molar ratio of acetylene reduced to nitrogen accumulated by the plants at the end of the experiment was 1.2 : 1. The significance of this value is discussed. Multiple use of the same plant material to study the time course of nitrogen fixation by the AR assay was found to be feasible under certain conditions.

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