The pattern of in situ summer nitrogenase activity in terrestrial Nostoc commune from Stipa–Bouteloa grassland, southern Alberta

1983 ◽  
Vol 61 (10) ◽  
pp. 2686-2693 ◽  
Author(s):  
D. S. Coxson ◽  
K. A. Kershaw
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Significant Proportion ◽  
Soil Surface ◽  
Nostoc Commune ◽  
Biological Fixation ◽  
Southern Alberta ◽  
Critical Moisture ◽  
Grassland Site

Field rates of nitrogenase activity by N. commune were followed over a 1-month summer period in Stipa–Bouteloa grassland of southern Alberta, using repeated short-term acetylene-reduction assays. Concurrent patterns of temperature, moisture, and light at the soil surface were continuously monitored. There is a rapid response of nitrogenase activity to both small precipitation events and dewfall hydration periods. Typically, thalli wet by thundershower activity in the previous evening showed a midday maximum of acetylene reduction of up to 5 nmol C2H4 mg−1 h−1, followed by a rapid cessation of activity as thalli desiccated below critical moisture levels. Over extended precipitation periods rates continue to climb throughout the day, gradually falling over the night period. Dry thalli frequently experience surface temperatures of up to 65 °C, without any discernable effects on rehydration recovery of nitrogenase activity. Equally, ground frosts early in the study period did not affect subsequent activity. Surface densities of up to 23.9 g m−2 were found for N. commune, with a mean cover of 4.3 g m−2. Mean cumulative nitrogen fixation over the 31-day field period was estimated to be 10.0 mg N m−2, although up to 77.3 mg N m−2 might be expected in localized microsites. The utilization of small rainfall events in large part accounts for the magnitude of observed nitrogenase activity. Although subsequent losses of fixed nitrogen through denitrification and volatilization are yet unknown, a significant proportion of nitrogen input to this grassland site must originate from asymbiotic biological fixation.

Nitrogenase activity during chinook snowmelt sequences by Nostoc commune in Stipa–Bouteloa grassland

1983 ◽  
Vol 29 (8) ◽  
pp. 938-944 ◽  
Author(s):  
D. S. Coxson ◽  
K. A. Kershaw
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Reduction Technique ◽  
Ambient Light ◽  
Nostoc Commune ◽  
Temperature Optimum ◽  
Active Radiation ◽  
Cumulative Activity ◽  
Southern Alberta ◽  
Field Activity

Inactivation of the nitrogenase enzyme in winter has been observed for many terrestrial cyanophytes of north temperate habitats. In southern Alberta frequent winter chinook activity causes repeated snowmelt sequences. The pattern of nitrogenase activity in these periods has been examined (acetylene-reduction technique) over several snowmelt periods. Nostoc collected from snowmelt pockets was immediately assayed for nitrogenase activity under laboratory (20 °C, 200 E∙m−2s−1 photosynthetically active radiation (PAR)) and field (ambient light and temperature) conditions. Air and thallus temperatures for a typical snowmelt sequence rose from −20 to +5 and −5 to +20 °C, respectively, as chinook warming progressed. Activity on initial snowmelt emergence was 420 nmol C2H4∙g−1∙h−1, rising to 1050 nmol after 7 h, monitored in lab conditions. Field activity reached 90 nmol after 4 h, ceasing at 1800 as temperatures fell below 0 °C. Laboratory rates at morning thaw, day 2, were 1040 nmol, while field activity (3 °C, 900 μE) was 800 nmol. By midday laboratory rates reached 1198 nmol, while field rates (10 °C, 1500 μE) were 1077 nmol. Although these rates are well below those at the temperature optimum of 35 °C (6805 nmol), clearly no winter inactivation of the nitrogenase enzyme occurs here. Cumulative activity over winter chinook sequences may well exceed that occurring during infrequent summer hydration.

Rehydration response of nitrogenase activity and carbon fixation in terrestrial Nostoc commune from Stipa–Bouteloa grassland

1983 ◽  
Vol 61 (10) ◽  
pp. 2658-2668 ◽  
Author(s):  
D. S. Coxson ◽  
K. A. Kershaw
Keyword(s):  
Respiratory Burst ◽  
Acetylene Reduction ◽  
Carbon Fixation ◽  
Light Exposure ◽  
Nitrogenase Activity ◽  
Net Photosynthesis ◽  
Rapid Decline ◽  
Carbon Dioxide Exchange ◽  
Nostoc Commune ◽  
Lower Temperature

The effects of wetting–drying cycles on patterns of carbon dioxide exchange and acetylene reduction were examined for colonies of the terrestrial cyanophyte Nostoc commune collected from a semiarid grassland site in southern Alberta, Canada. At 14 and 21 °C acetylene reduction takes ca. 14 h to resume maximal rates, although activity is detected within minutes of rehydration. Net photosynthesis reaches compensation minutes after rehydration and is maximal in under 80 min at 21 °C. No respiratory burst is evident, either for replicates previously dried rapidly (0.5 h) or slowly (5 h). In marked contrast, however, at 7 °C only minimal recovery of acetylene reduction is evident after 48 h diurnal treatment, while net photosynthesis requires a recovery time of 6 h. Again no respiratory burst is evident. After rehydration, the magnitude of acetylene reduction is strongly dependent on both the previous illumination level and temperature. The rapid decline in activity on transfer to darkness or on addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea can be moderated by increasing the duration of the previous light exposure or by incubation at lower temperature. This suggests the presence of substrate pools, the replenishment of which by photosynthesis allows oxidative phosphorylative support of nitrogenase activity in the dark. The extreme resistance of N. commune to desiccation and heat stress combined with its ability to resume metabolic activity within minutes of wetting should allow very effective utilization of small precipitation events during the summer months. The slower recovery of nitrogenase activity upon rehydration at lower temperatures may restrict winter field activity on rare occasions when thalli become dehydrated between snowfall periods.

A survey of angiosperms in Nova Scotia for rhizosphere nitrogenase (acetylene-reduction) activity

1978 ◽  
Vol 56 (18) ◽  
pp. 2218-2223 ◽  
Author(s):  
D. Smith ◽  
D. G. Patriquin
Keyword(s):  
Nova Scotia ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Reduction Technique ◽  
Acetylene Reduction Activity ◽  
Forage Grasses ◽  
Reduction Activity ◽  
Tropical Forage ◽  
Poorly Drained Soils

Excised root samples from 901 plants, representing 130 species of nonnodulated angiosperms largely in upland, pioneering habitats, were assayed for nitrogenase activity by the acetylene-reduction technique after overnight preincubation of the samples under low pO2. Most samples and most species exhibited very low excised root acetylene-reducing activities, but for 19 species, maximum values were greater than 50 nmol C2H4∙g−1∙h−1. In situ C2H2 assays, conducted on 10 species which had exhibited maximum excised root activities greater than 10 nmol C2H4∙g−1∙h−1, indicated average belowground N2-fixation rates of 3 to 92 g N∙ha−1∙day−1 and maxima greater than 100 g N∙ha−1∙day−1 for 3 of the 10 species. The highest values were for grasses characteristic of poorly drained soils and for some dicotyledonous weeds. It is concluded that the potential of temperate-zone angiosperms for nitrogenase activity by 'associative symbioses' approaches that of tropical forage grasses.

Conversion factor between acetylene reduction and nitrogen fixation in free-living cyanobacteria from high arctic habitats

1999 ◽  
Vol 45 (3) ◽  
pp. 223-229 ◽  
Author(s):  
Turid Liengen
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Conversion Factor ◽  
Soil Surface ◽  
High Arctic ◽  
Acetylene Reduction Activity ◽  
Nostoc Commune ◽  
Free Living ◽  
Conversion Factors ◽  
N Incorporation

The conversion factor between acetylene reduction and15N incorporation in free-living cyanobacteria was determined in different high arctic habitats in the area of Ny-Ålesund (78.5°N, 11.6°E), Spitsbergen, in the summer of 1994. The experiments were carried out under constant conditions, 19°C and 200 µE·m-2·s-1. The nitrogen-fixation activities, measured as15N-incorporation, were in the range 4.01-6.54 mg N2fixed·gdw-1·day-1(dw, dry weight) in sheets of Nostoc commune and 778-1206 mg N2fixed·m-2·day-1in the cyanobacterial crusts. The acetylene reduction activities were in the range 0.72-1.91 mg ethylene produced·gdw-1·day-1of N. commune and 12.8-63.7 mg ethylene produced·m-2·day-1in the cyanobacterial crusts. The conversion factor of N. commune ranged from 0.11 to 0.48 for ethylene produced to nitrogen fixed, whereas the cyanobacterial crusts covering the soil surface gave conversion factors in the range 0.022-0.073 for ethylene produced to nitrogen fixed. An Anabaena sp., isolated from one of the habitats investigated, gave conversion factors near the theoretical factor of 4, when determined at 14.0 and 17.3°C. It was concluded that the acetylene reduction activity of free-living cyanobacteria in high arctic habitats results in underestimates of the real nitrogen-fixation activity in these environments.Key words: nitrogen fixation, acetylene reduction, conversion factor, cyanobacteria, Nostoc commune, high arctic.

Effects of the length of incubation period and herbicides on nitrogenase activity of pea (Pisum sativum L.)

2002 ◽  
Vol 50 (2) ◽  
pp. 135-143
Author(s):  
G. Singh ◽  
Keyword(s):  
Pisum Sativum ◽  
Incubation Period ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Pot Experiment ◽  
Flowering Stage ◽  
Seed Filling ◽  
Pisum Sativum L ◽  
Reduction Assay

In a pot experiment the effects of the length of incubation period and the pre-emergence application of terbutryn/terbuthylazine at 2.80 kg a.i. ha-1 or post-emergence application of bentazone at 2.88 kg a.i. ha-1 on the nitrogenase activity in intact pea plants were measured in situ by the acetylene reduction assay. An incubation period of 10 min resulted in the highest nitrogenase activity. As the length of the incubation period increased to 30 or 60 min the total as well as the specific nitrogenase activity decreased. Terbutryn/terbuthylazine decreased the total nitrogenase activity at all three (i.e. vegetative, flowering and seed-filling) stages, whereas bentazone resulted in a significant decrease at the flowering stage only. However, terbutryn/terbuthylazine-treated plants had the highest specific nitrogenase activity both at the flowering and seed-filling stages.

scholarly journals Rock Surface Fungi in Deep Continental Biosphere—Exploration of Microbial Community Formation with Subsurface In Situ Biofilm Trap

2020 ◽  
Vol 9 (1) ◽  
pp. 64
Author(s):  
Maija Nuppunen-Puputti ◽  
Riikka Kietäväinen ◽  
Lotta Purkamo ◽  
Pauliina Rajala ◽  
Merja Itävaara ◽  
...  
Keyword(s):  
Significant Proportion ◽  
Debaryomyces Hansenii ◽  
Fungal Communities ◽  
Fungal Colonization ◽  
Rock Surface ◽  
Mica Schist ◽  
Deep Subsurface ◽  
Bacterial Phyla ◽  
In Situ Conditions

Fungi have an important role in nutrient cycling in most ecosystems on Earth, yet their ecology and functionality in deep continental subsurface remain unknown. Here, we report the first observations of active fungal colonization of mica schist in the deep continental biosphere and the ability of deep subsurface fungi to attach to rock surfaces under in situ conditions in groundwater at 500 and 967 m depth in Precambrian bedrock. We present an in situ subsurface biofilm trap, designed to reveal sessile microbial communities on rock surface in deep continental groundwater, using Outokumpu Deep Drill Hole, in eastern Finland, as a test site. The observed fungal phyla in Outokumpu subsurface were Basidiomycota, Ascomycota, and Mortierellomycota. In addition, significant proportion of the community represented unclassified Fungi. Sessile fungal communities on mica schist surfaces differed from the planktic fungal communities. The main bacterial phyla were Firmicutes, Proteobacteria, and Actinobacteriota. Biofilm formation on rock surfaces is a slow process and our results indicate that fungal and bacterial communities dominate the early surface attachment process, when pristine mineral surfaces are exposed to deep subsurface ecosystems. Various fungi showed statistically significant cross-kingdom correlation with both thiosulfate and sulfate reducing bacteria, e.g., SRB2 with fungi Debaryomyces hansenii.

Estimating Nitrogenase Activity of Faba Bean (Vicia faba) by Acetylene Reduction (Ar) Assay

1990 ◽  
Vol 17 (5) ◽  
pp. 489 ◽  
Author(s):  
Herdina ◽  
JH Silsbury
Keyword(s):  
Diurnal Variation ◽  
Vicia Faba ◽  
Faba Bean ◽  
Closed System ◽  
N2 Fixation ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Electron Flow ◽  
Specific Rate ◽  
Rooting Medium

Methods of conducting acetylene reduction (AR) assay were appraised for estimating the nitrogenase activity of nodules of faba bean (Vicia faba L.). Factors considered were: (i) disturbance of plants when removing the rooting medium; (ii) assay temperature; (iii) the use of whole plants rather than detached, nodulated roots; (iv) diurnal variation in nodule activity; and (v) a decline in C2H4 production after exposure to C2H2. Plants growing in jars of 'oil dry' (calcined clay) had the same AR activity when assayed in situ in a closed system as when assayed after removal of the rooting medium. Assay temperatures of 12.5, 17.5 and 22.5°C influenced the specific rate of AR with the optimum at 17.5°C. Removal of the shoot resulted in a rapid decrease in AR activity in both vegetative and reproductive plants but the effect was much larger in the latter. AR and respiration by nodulated roots were closely linked and both varied markedly over a diurnal 12 h/12 h cycle. Since no fluctuation was found after nodules were detached, diurnal variation in the respiration of nodulated roots is attributed to change in nodule activity. Half of the dark respiration of nodulated roots was associated with respiration of the nodules and thus largely with N2 fixation. Since the AR assay provides no information on how electron flow in vivo is partitioned between reduction of N2 and reduction of protons, diurnal variation in hydrogen evolution (HE) in air and Ar/O2 in an open system was used to estimate this partitioning. Diurnal variation in apparent N2 fixation estimated in this manner was examined at a 'low' PPFD (300 μmol m-2 s-1) and at 'high' (1300 μmol m-2 s-1) to explore whether variation could be attributed to change in carbohydrate supply. Although HE in air and in Ar/O2 were both closely linked with the respiration of the nodulated root, apparent N2 fixation showed only a slight diurnal variation at 'low' light and almost none at 'high'. Vegetative plants showed no C2H2-induced decline in activity with exposure to C2H2 but reproductive plants did. This difference appears to be an age effect rather than attributable to flowering per se, since a decline occurred even when plants were kept vegetative by disbudding. A closed system for AR assay appears satisfactory for vegetative faba bean but such an assay over a 40-min period during the reproductive stage would underestimate nitrogenase activity by about 20%.

Dinitrogen fixation and nodulation by Frankia in Alnus incana as affected by inorganic nitrogen in pot experiments with peat

1983 ◽  
Vol 61 (11) ◽  
pp. 2956-2963 ◽  
Author(s):  
U. Granhall ◽  
T. Ericsson ◽  
M. Clarholm
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Inorganic Nitrogen ◽  
Experimental Period ◽  
Alnus Incana ◽  
Nitrogen Application ◽  
Noticeable Effect ◽  
Essential Nutrients ◽  
Pot Experiments ◽  
Ph Level

The effects of single large or repeated, exponentially increasing applications of nutrients, with or without inorganic nitrogen and at two pH levels, on the growth, nodulation, acetylene reduction, and nutrient uptake in Alnus incana (L.) Moench were investigated in pot experiments with peat under controlled laboratory conditions. The repeated application of inorganic nitrogen did not suppress nitrogenase activity until the last 2 weeks, whereas an initial, large, nitrogen application effectively inhibited nodulation and activity throughout the 40-day experimental period. The mode of nitrogen application was thus found to be more important than the total amounts applied. Shoot length, leaf area, shoot–root relations, dry-matter production, and nitrogen contents of plants were determined at the end of the experiment, as well as the effect of Frankia inoculations. Nitrogenase activity was determined three times, at 0, 3, and 5 weeks. N2 fixation (balance/acetylene reduction) was found to be maximal, 55% of total nitrogen uptake, in minus-N pots with single applications of essential nutrients. The fastest growth was, however, noted in pots with single applications of all nutrients, including N. Among the latter, pots inoculated with Frankia showed the best growth, in spite of low nitrogenase activity. The only noticeable effect of a raised pH level was a reduced endophyte activity in minus-N pots with single applications of essential nutrients, due to increased N mineralization in the peat.

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