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.

Nitrogen Fixation on a Tropical Volcano, La Soufrière (Guadeloupe): The Interaction of Temperature, Moisture, and Light with Net Photosynthesis and Nitrogenase Activity in Stereocaulon Virgatum and Response to Periods of Insolation Shock

1988 ◽  
Vol 20 (1) ◽  
pp. 63-81 ◽  
Author(s):  
R. P. Fritz-Sheridan ◽  
D. S. Coxson
Keyword(s):  
Quantum Yield ◽  
Light Intensity ◽  
Acetylene Reduction ◽  
Light Exposure ◽  
Nitrogenase Activity ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
High Light Intensity ◽  
High Light ◽  
Apparent Quantum Yield

AbstractThe response of net photosynthesis, dark respiration and acetylene reduction to temperature, moisture and light intensity were examined for Stereocaulon virgatum growing in the cloud/shroud zone on the tropical volcano La Soufrière, Guadeloupe, French West Indies. Rates for both acetylene reduction and net photosynthesis were maximal at saturating water contents, a pattern attributed to the finely branched nature of the phyllocladoid branchlets and the exposed position of spherical cephalodia, both of which minimize the formation of surface and interhyphal water films. Under conditions typical of those during cloud/shroud periods (13–16°C), thalli of S. virgatum exhibit many characteristics seen in other shade-tolerant lichen species. Net photosynthesis was light saturated at 300 μmol m−2 s−1 PAR, while the photocompensation point was less than 25 µmol m−2 s−1 PAR. Net photosynthetic uptake of carbon dioxide was optimal at 27–34°C, at which point light saturation was near 700 µmol m−2 s−1 PAR and the photocompensation point between 50 and 100 µmol m−2 s−1 PAR. Thalli of S. virgatin exhibited temperature-dependent sensitivity to high insolation. Only at 20°C were thalli able to tolerate high light exposure without reduction of apparent quantum yield. Exposure to high light intensity at 40°C inhibited the apparent quantum yield by almost 40% and acetylene reduction by 95%. This suggests brief periods of insolation shock may exert an influence disproportionately higher than either their frequency or duration. Thalli are normally exposed to cloud/shroud conditions but net photosynthetic uptake was maximal only during periods of elevated thallus temperature experienced at the onset of an insolation shock. However, with prolonged high insolation exposure and further elevation of thallus temperatures and thallus desiccation, severe impairment of subsequent photosynthetic activity ensues. S. virgatum may be characterized as a shade-tolerant species but its physiology is more adapted in some respects to conditions experienced during rare periods of full insolation.

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.

Physiological acclimations to chilling temperature in symbiotically grown alfalfa

1989 ◽  
Vol 67 (2) ◽  
pp. 352-359 ◽  
Author(s):  
F. D. H. Macdowall ◽  
D. B. Layzell ◽  
K. B. Walsh ◽  
A. S. Denes
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Cold Treatment ◽  
Rest Period ◽  
Net Photosynthesis ◽  
Temperature Profiles ◽  
Whole Plant ◽  
Flow Through ◽  
Nodulated Root ◽  
Whole Plants

An apparent shoot rest period was induced in the 2nd month of growth of alfalfa (Medicago sativa L.) seedlings by a drop in growth temperature from 25:20 °C to 10:7 °C. After prolonged chilling the shoots were replaced by new shoots. Temperature profiles of nodulated root respiration and nitrogenase activity (acetylene reduction and H2 evolution) were measured simultaneously in experiments with a flow-through gassing system during 3 months of cold treatment. Net photosynthesis of whole plants was measured in a closed system. More than half the total initial nitrogenase activity and relative efficiency (RE) were lost during the rest period and recovered during regrowth. Acetylene reduction by chilled plants was insensitive to temperature in the 5 – 15 °C range, unlike the temperature dependence of respiration and H2 evolution in air. In all temperature profiles of RE the RE was highest at 5 – 10 °C. The RE was minimum 10 – 15 °C during the rest period. The optimum temperature for whole plant net photosynthesis also declined to 10 – 15 °C during chilling and it later flattened out in the cold-acclimated regrowth. Possible mechanisms are discussed.

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.

scholarly journals Measurement of Carbon Fixation and Allocation Using 11C-Labeled Carbon Dioxide

Radiocarbon ◽  
1983 ◽  
Vol 25 (2) ◽  
pp. 441-446 ◽  
Author(s):  
Boyd R Strain ◽  
John D Goeschl ◽  
Charles H Jaeger ◽  
Youhanna Fares ◽  
Charles E Magnuson ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Carbon Fixation ◽  
Dark Respiration ◽  
Net Photosynthesis ◽  
Time Measurement ◽  
Carbon Dioxide Exchange ◽  
Carbon Dioxide Assimilation ◽  
Real Time Measurement ◽  
Infra Red ◽  
The Subject

The real-time measurement of net photosynthesis and dark respiration of plants has been possible since the development of the infra-red analyzer and its application in the 1940's. This technique has allowed intensive investigations of the mechanisms and dynamics of carbon dioxide assimilation by green plants (Sestak, Catsky, and Jarvis, 1971). As a result, physiologic and ecologic aspects of net carbon dioxide exchange are the subject of much research (eg, Osmond, Bjorkman and Anderson, 1980).

Temporal changes in carbon dioxide exchange rates, acetylene reduction and distribution of nitrogen in Barrel Medic (Medicago trunculata Gaertn.) grown in the field

1986 ◽  
Vol 37 (3) ◽  
pp. 263 ◽  
Author(s):  
AM Alston ◽  
DW Puckridge
Keyword(s):  
Carbon Dioxide ◽  
Exchange Rates ◽  
Nitrogen Content ◽  
Environmental Conditions ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Carbon Dioxide Exchange ◽  
Plant Nitrogen ◽  
Barrel Medic

Barrel medic (cv. Jemalong) was grown on a red-brown earth at Adelaide to examine dry matter production and nitrogenase activity in relation to environmental conditions and carbon dioxide exchange. At 4-10-day intervals, measurements were made of dry weight and nitrogen content in plant parts, and mineral nitrogen content of the soil. Rates of acetylene reduction and carbon dioxide exchange, and environmental variables were measured. Curves fitted to data for solar radiation and carbon exchange rate were used to calculate daily values for net carbon dioxide uptake. Estimates of dry weight production derived from these net uptakes of carbon dioxide gave a similar curve to measured dry weight, but overestimated maximum dry weight by almost 20%. The difference is presumed to be due to materials lost from the roots. At maturity, dry weight and plant nitrogen content had declined by 10 and 14% respectively from their maxima of 1.02 kg m-2 and 26.1 g m-2 in October. All fractions of the plant except the litter and seed lost nitrogen. Rates of acetylene reduction reached a maximum of 39 mmol m-2 day-1 104 days from sowing, when the medic began to flower, and declined to almost zero by 145 days. At this time carbon dioxide exchange rates were high, and the plants were still accumulating nitrogen; from approximately 14 g N m-2 at day 104 to 24 g N m-2 at day 145. These changes are discussed in relation to environmental conditions and soil nitrogen content.

scholarly journals Ecophysiological characterization of early successional biological soil crusts in heavily human-impacted areas

2018 ◽  
Vol 15 (7) ◽  
pp. 1919-1931 ◽  
Author(s):  
Michelle Szyja ◽  
Burkhard Büdel ◽  
Claudia Colesie
Keyword(s):  
Carbon Fixation ◽  
Climatic Factors ◽  
Net Photosynthesis ◽  
Biological Soil Crusts ◽  
Taxonomic Composition ◽  
Nostoc Commune ◽  
Fixation Rate ◽  
Soil Crusts ◽  
Disturbed Areas ◽  
A Minor

Abstract. Ecophysiological characterizations of photoautotrophic communities are not only necessary to identify the response of carbon fixation related to different climatic factors, but also to evaluate risks connected to changing environments. In biological soil crusts (BSCs), the description of ecophysiological features is difficult, due to the high variability in taxonomic composition and variable methodologies applied. Especially for BSCs in early successional stages, the available datasets are rare or focused on individual constituents, although these crusts may represent the only photoautotrophic component in many heavily disturbed ruderal areas, such as parking lots or building areas with increasing surface area worldwide. We analyzed the response of photosynthesis and respiration to changing BSC water contents (WCs), temperature and light in two early successional BSCs. We investigated whether the response of these parameters was different between intact BSC and the isolated dominating components. BSCs dominated by the cyanobacterium Nostoc commune and dominated by the green alga Zygogonium ericetorum were examined. A major divergence between the two BSCs was their absolute carbon fixation rate on a chlorophyll basis, which was significantly higher for the cyanobacterial crust. Nevertheless, independent of species composition, both crust types and their isolated organisms had convergent features such as high light acclimatization and a minor and very late-occurring depression in carbon uptake at water suprasaturation. This particular setup of ecophysiological features may enable these communities to cope with a high variety of climatic stresses and may therefore be a reason for their success in heavily disturbed areas with ongoing human impact. However, the shape of the response was different for intact BSC compared to separated organisms, especially in absolute net photosynthesis (NP) rates. This emphasizes the importance of measuring intact BSCs under natural conditions for collecting reliable data for meaningful analysis of BSC ecosystem services.

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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