Dinitrogen fixation by a mature Ceanothus velutinus (Dougl.) stand in the Western Oregon Cascades

1983 ◽  
Vol 29 (8) ◽  
pp. 1014-1021 ◽  
Author(s):  
D. H. McNabb ◽  
K. Cromack Jr.
Keyword(s):  
Nitrogenase Activity ◽  
Dinitrogen Fixation ◽  
Total Biomass ◽  
Fixation Rate ◽  
Xylem Pressure ◽  
Nodule Biomass ◽  
Oregon Cascades ◽  
Mature Stands ◽  
Large Nodule ◽  
Precipitation Events

Dinitrogen fixation was measured in a 17-year-old snowbrush, Ceanothus velutinus var. velutinus (Dougl.), stand in the Western Oregon Cascades. Diurnal and seasonal rates of nitrogenase activity were measured in the field using the C2H2 reduction technique. Snowbrush had a total biomass, estimated with equations developed, of 42 680 kg∙ha−1, including 750 kg∙ha−1 of nodule biomass. Snowbrush fixed N2 for approximately 240 days annually. Except during precipitation events or periods of low xylem pressure potentials, C2H2 reduction rates in the summer and fall were significantly correlated with soil temperature (R2 = 0.93**, n = 6). A diurnal variation in nitrogenase activity also was measured. The annual N2 fixation rate was estimated at approximately 101 kg N∙ha−1 (C2H2). Sustained periods of precipitation suppressed nitrogenase activity and reduced the estimate by about 19%. The annual N2 fixation rate is higher than previously reported for other mature stands and primarily is attributed to the maintenance of a large nodule biomass.

scholarly journals Bacterial Life and Dinitrogen Fixation at a Gypsum Rock

2004 ◽  
Vol 70 (12) ◽  
pp. 7070-7077 ◽  
Author(s):  
Gudrun Boison ◽  
Alexander Mergel ◽  
Helena Jolkver ◽  
Hermann Bothe
Keyword(s):  
Nitrogenase Activity ◽  
Dinitrogen Fixation ◽  
Molecular Techniques ◽  
Low Light ◽  
Light Intensities ◽  
Bluish Green ◽  
Reductase Gene ◽  
Gypsum Rock ◽  
Microaerobic Conditions ◽  
Reduced Light

ABSTRACT The organisms of a bluish-green layer beneath the shards of a gypsum rock were characterized by molecular techniques. The cyanobacterial consortium consisted almost exclusively of Chroococcidiopsis spp. The organisms of the shards expressed nitrogenase activity (C2H2 reduction) aerobically and in light. After a prolonged period of drought at the rock, the cells were inactive, but they resumed nitrogenase activity 2 to 3 days after the addition of water. In a suspension culture of Chroococcidiopsis sp. strain PCC7203, C2H2 reduction required microaerobic conditions and was strictly dependent on low light intensities. Sequencing of a segment of the nitrogenase reductase gene (nifH) indicated that Chroococcidiopsis possesses the alternative molybdenum nitrogenase 2, expressed in Anabaena variabilis only under reduced O2 tensions, rather than the widespread, common molybdenum nitrogenase. The shards apparently provide microsites with reduced light intensities and reduced O2 tension that allow N2 fixation to proceed in the unicellular Chroococcidiopsis at the gypsum rock, unless the activity is due to minute amounts of other, very active cyanobacteria. Phylogenetic analysis of nifH sequences tends to suggest that molybdenum nitrogenase 2 is characteristic of those unicellular or filamentous, nonheterocystous cyanobacteria fixing N2 under microaerobic conditions only.

Seasonal variation in nitrogen fixation, associated microbial populations, and carbohydrates in roots and rhizomes of Typha latifolia (Typhaceae)

1984 ◽  
Vol 62 (9) ◽  
pp. 1965-1967 ◽  
Author(s):  
David D. Biesboer
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Anaerobic Bacteria ◽  
Typha Latifolia ◽  
Root Surface ◽  
Microbial Populations ◽  
Aerobic Bacteria ◽  
Free Sugar ◽  
Fixation Rate ◽  
Reduction Assay

Seasonal changes in nitrogen fixation, numbers of nitrogen-fixing bacteria associated with the roots, and rhizome–root carbohydrates were studied for the broad-leaved cattail, Typha latifolia L. Populations of anaerobic and aerobic diazotrophic bacteria were present on the root surface. Anaerobic bacteria predominated in the diazotrophic association, were more active in the acetylene reduction assay, and generally outnumbered aerobic bacteria by 2 to 1 during maximum rates of seasonal nitrogen fixation. The observed maximum nitrogen fixation rate coincided closely with reproductive development in Typha and peak microbial populations. Starch levels in rhizomes were nearly depleted during the middle of the growing season, whereas free sugar concentrations remained stable. Sugar concentrations in the roots increased rapidly during rhizome–root growth and decreased rapidly prior to peak nitrogenase activity.

Symbiotic Nitrogen Fixation by Coralloid Roots of the Cycad Macrozamia riedlei: Physiological Characteristics and Ecological Significance

1976 ◽  
Vol 3 (3) ◽  
pp. 349 ◽  
Author(s):  
J Halliday ◽  
JS Pate
Keyword(s):  
Nitrogenase Activity ◽  
Natural Habitat ◽  
Natural Populations ◽  
Molar Ratio ◽  
Fixation Rate ◽  
Plant Nitrogen ◽  
Blue Green Algae ◽  
C2h2 Reduction ◽  
Whole Plant ◽  
Coralloid Roots

'Coralloid' roots containing blue-green algae occur commonly on the upper root stocks of M. riedlei in natural habitat in Western Australia. Each coralloid mass persists for several seasons; replacement sets form at irregular intervals, especially after fire. 15N2 and acetylene reduction assays demonstrate that coralloid roots fix nitrogen at physiologically significant rates. C2H2 reduction rates by coralloid roots are higher in winter than in summer. Performance is positively correlated with rainfall; soil temperature appears to be of lesser importance. Diurnal fluctuations in nitrogenase activity occur. Calibration using 15N2 gives a molar ratio of C2H2 reduced : N2 fixed of 5.8 : 1. The seasonal average of C2H2 reduction of 14.8 nmol per g fresh wt coralloid root per min is then equivalent to 37.6 g N per kg fresh wt per year, a fixation rate potentially capable of doubling coralloid root nitrogen once in every 8 weeks, and whole plant nitrogen every 8-11 years. Returns of fixed nitrogen in two natural populations of Macrozamia are estimated by compounding measurements of biomass of host and symbiotic organs with the seasonal average for coralloid fixation rate. The values obtained (18.8 and 18.6 kg N ha-1 year-1) indicate that Macrozamia contributes significantly to the nitrogen economy of its ecosystem.

Rhodolith holobionts are not sources of fixed nitrogen in a northeastern Gulf of Mexico patch reef

2020 ◽  
Author(s):  
Ethan C Cissell ◽  
Sven A Kranz ◽  
Sophie J McCoy
Keyword(s):  
Nitrogen Fixation ◽  
Gulf Of Mexico ◽  
Nitrogenase Activity ◽  
Patch Reef ◽  
Dry Mass ◽  
Fixation Rate ◽  
Northeastern Gulf Of Mexico ◽  
Local Ecosystem ◽  
Water Column Nutrient ◽  
Functional Analyses

Rhodoliths provide numerous benefits to coastal ecosystems and help support high biodiversity. No study, however, has explored rhodoliths that occupy northeastern Gulf of Mexico patch reefs, and their contributions to local ecosystem function remain uncharacterized. Here, we employed the acetylene reduction assay to assess nitrogen fixation capability in rhodolith holobionts (Lithothamnion spp.; Rhodophyta), sediment, and surrounding seawater from a subtropical patch reef ecosystem in the northeastern Gulf of Mexico. We found no evidence for nitrogenase activity in rhodolith holobionts or seawater from our study site, while nitrogenase activity in sediment underlying rhodoliths was approximately equivalent to a nitrogen fixation rate of 0.521 (SD 0.087) nmol N2 g dry mass−1 hr−1. Our results suggest that rhodoliths in the northeastern Gulf of Mexico rely on sources of nitrogen from sediment nitrogen fixation or water column nutrient availability rather than the activity of symbiotic diazotrophic microorganisms. Functional analyses recognizing rhodoliths as holobionts warrant further investigation to better understand the ecology of rhodoliths.

Seasonal patterns of root nodule growth, endophyte morphology, nitrogenase activity, and shoot development in Myrica gale

1982 ◽  
Vol 60 (6) ◽  
pp. 746-757 ◽  
Author(s):  
Christa R. Schwintzer ◽  
Alison M. Berry ◽  
Lynn D. Disney
Keyword(s):  
Root Nodule ◽  
Nitrogenase Activity ◽  
Shoot Development ◽  
Infected Tissue ◽  
Actinorhizal Plants ◽  
Seasonal Patterns ◽  
Cortical Cells ◽  
Myrica Gale ◽  
Nodule Biomass ◽  
Infected Cells

Myrica gale L. populations growing in central Massachusetts were observed throughout the ice-free season. Nitrogenase activity appeared in mid-May shortly after budbreak, was at its maximum between late June and mid-August, and disappeared in late October after all leaves had fallen. Growth of overwintering nodules began in early May and was largely complete by mid-July. Most nodules (88%) lived for 3 years or less and 61% of the nodule biomass present in autumn was produced during the current season.Colonizing hyphae of the Frankia sp. endophyte were seen throughout the year in partially expanded cortical cells near the nodule lobe apex. Vesicles first appeared in mature cortical cells coincident with the onset of nitrogenase activity in mid-May, occupied the bulk of the infected tissue during the summer, and disappeared as nitrogenase activity ceased in late October. Evidence is presented that the vesicles are the site of nitrogenase activity and are newly produced each season in freshly formed nodule lobe tissue. Sporangia frequently formed in mature infected cells in nodules at one site but were rare at another. The processes described here in M. gale are probably typical of winter-deciduous actinorhizal plants.

scholarly journals The impact of a native hemiparasite on a major invasive shrub is affected by host size at time of infection

2020 ◽  
Vol 71 (12) ◽  
pp. 3725-3734
Author(s):  
Robert M Cirocco ◽  
José M Facelli ◽  
Jennifer R Watling
Keyword(s):  
Root Biomass ◽  
Isotope Composition ◽  
Nitrogen Concentration ◽  
Host Size ◽  
Quantum Yields ◽  
Total Biomass ◽  
Invasive Shrub ◽  
Ulex Europaeus ◽  
Nodule Biomass ◽  
The Impact

Abstract Many studies have investigated the effect of parasitic plants on their hosts; however, few have examined how parasite impact is affected by host size. In a glasshouse experiment, we investigated the impact of the Australian native hemiparasitic vine, Cassytha pubescens, on a major invasive shrub, Ulex europaeus, of different sizes. Infected plants had significantly lower total, shoot, and root biomass, but the parasite’s impact was more severe on small than on large hosts. When infected, small but not large hosts had significantly lower nodule biomass. Irrespective of size, infection significantly decreased the host shoot/root ratio, pre-dawn and midday quantum yields, maximum electron transport rates, and carbon isotope composition, and the host nodule biomass per gram of root biomass significantly increased in response to infection. Infection did not affect host foliar nitrogen concentration or midday shoot water potential. Parasite biomass was significantly lower on small relative to large hosts, but was similar when expressed on a per gram of host total biomass basis. Parasite stem nitrogen, phosphorus, and potassium concentrations were significantly greater when C. pubescens was growing on small than on large hosts. Our results clearly show that C. pubescens strongly decreases performance of this major invasive shrub, especially when hosts are small. This suggests that C. pubescens could be used most effectively as a native biocontrol when deployed on smaller hosts.

Nodule biomass and acetylene reduction rates of red alder and Sitka alder on Vancouver Island, B.C.

1981 ◽  
Vol 11 (2) ◽  
pp. 282-287 ◽  
Author(s):  
Dan Binkley
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Reduction Rate ◽  
Vancouver Island ◽  
Fixation Rate ◽  
Red Alder ◽  
Nodule Biomass ◽  
Closed Canopy ◽  
Management Alternative ◽  
Acetylene Reduction Rate

Three comparisons examined acetylene reduction rate and nodule biomass of red alder (Alnusrubra Bong.) and Sitka alder (Alnussinuata (Regel) Rydb.) on Vancouver Island, British Columbia. The first showed that the acetylene reduction rates of Sitka alder on four sites in early July 1979 varied from 8.8 to 22.0 μmol C2H2•g−1 dry nodule per hour; smaller nodules had the higher rates. In the second comparison, red alder and Sitka alder acetylene reduction rates for young plants were similar when assayed on the same day on the same site. Finally, acetylene reduction rates and nodule biomass were determined for both species growing in closed canopy stands on adjacent sites. In this pair of 20-year-old stands, red alder had double the acetylene reduction rate and three times the nodule biomass of the Sitka alder. Combining the nodule biomass estimates with the seasonal average reduction rates yielded current annual nitrogen fixation estimates (using C2H2) of 130 kg•ha−1•year−1 for the red alder plot and 20 kg•ha−1•year−1 for the Sitka alder plot. These estimates are within published ranges for the species. The lower fixation rate of Sitka alder is still substantial, relative to the nitrogen demands of conifers, and its shrub-like growth form makes it an attractive management alternative to red alder for biological nitrogen fixation in mixed conifer–alder plantations.

Changes in dinitrogen fixation in maturing stands of Casuarinaequisetifolia and Leucaenaleucocephala

1996 ◽  
Vol 26 (9) ◽  
pp. 1684-1691 ◽  
Author(s):  
John A. Parrotta ◽  
Dwight D. Baker ◽  
Maurice Fried
Keyword(s):  
Weighted Average ◽  
Single Species ◽  
Dinitrogen Fixation ◽  
Total Biomass ◽  
Reference Species ◽  
Mixed Species ◽  
Available Nitrogen ◽  
Enrichment Technique ◽  
N Enrichment ◽  
Whole Tree

Biological dinitrogen fixation in Casuarinaequisetifolia J.R. & G. Forst. and Leucaenaleucocephala (Lam.) de Wit was evaluated using the 15N-enrichment technique under field conditions in single-species and mixed-species plantings (with a nonfixing reference species, Eucalyptus ×robusta J.E. Smith) between 1.0 and 3.5 years of age in Puerto Rico. Following periodic labelling of trenched and untrenched plantation quadrats with 15N-enriched ammonium sulfate, analyses of foliar and whole-tree (weighted average) N-isotopic ratios and total biomass N were used to estimate the proportion of nitrogen derived from biological dinitrogen fixation (PNDFA) and total nitrogen derived from fixation (TNDFA) in C. equisetifolia and L. leucocephala. The 15N-enrichment technique yielded accurate estimates of dinitrogen fixation in maturing stands of these two tree species provided the reference species (Eucalyptus) was grown in close proximity to the N-fixing species in trenched, mixed-species plots. Changes in the 15N/14N ratio of soil-available nitrogen in single-species plots of the N-fixing and reference were found to yield inaccurate estimates of dinitrogen fixation in the single-species plots of C. equisetifolia and L. leucocephala after 2 years of age. The results confirm earlier findings that foliar sampling is a useful nondestructive alternative to whole-tree biomass sampling for the 15N-enrichment protocol. Between 1.0 and 3.5 years after plantation establishment, PNDFA in C. equisetifolia remained relatively constant between 50 and 60%, while PNDFA in L. leucocephala declined from nearly 100% at 1 year to less than 40% at 3.5 years. The rate of dinitrogen fixation (kg•ha−1•year−1) did not decline as the stands matured. Cumulative dinitrogen fixation (TNDFA) estimates at 3.5 years were very similar between species: 73 in C. equisetifolia and 74 kg N•ha−1•year−1 in L. leucocephala.

Nodulation and dinitrogen fixation of legume trees in a tropical freshwater swamp forest in French Guiana

2003 ◽  
Vol 19 (6) ◽  
pp. 655-666 ◽  
Author(s):  
Piia Koponen ◽  
Pekka Nygren ◽  
Anne Marie Domenach ◽  
Christine Le Roux ◽  
Etienne Saur ◽  
...  
Keyword(s):  
French Guiana ◽  
Nitrogenase Activity ◽  
Basal Area ◽  
Dinitrogen Fixation ◽  
Bacterial Strains ◽  
Swamp Forest ◽  
Legume Trees ◽  
Freshwater Swamp ◽  
Tropical Freshwater

Nodulated legume trees comprised 43% of the stand basal area in the low, most frequently flooded microsites, and 23% in higher, drier microsites in a tropical freshwater swamp forest in French Guiana. Dinitrogen fixation in Pterocarpus officinalis, Hydrochorea corymbosa and Inga pilosula was confirmed by acetylene reduction assay (ARA), presence of leghaemoglobin in nodules and the 15N natural abundance method. The results for Zygia cataractae were inconclusive but suggested N2 fixation in drier microsites. Nodulated Inga disticha had a 15N-to-14N ratio similar to non-N2-fixing trees, but ARA indicated nitrogenase activity and leghaemoglobin was present in nodules. All bacterial strains were identified as Bradyrhizobium spp. according to the partial 16S rDNA sequences, and they were infective in vitro in the model species Macroptilium atropurpureum. About 35-50% of N in the leaves of P. officinalis, H. corymbosa and I. pilosula was fixed from the atmosphere. Dinitrogen fixation was estimated to contribute at least 8-13% and 17-28% to whole-canopy N in high and low microsites, respectively. Symbiotic N2 fixation appears to provide both a competitive advantage to legume trees under N-limited, flooded conditions and an important N input to neotropical freshwater swamp forests.

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