Cultivar differences in assimilate partitioning and capacity to maintain N2 fixation rate in pea during pod-filling

1992 ◽  
Vol 139 (2) ◽  
pp. 185-194 ◽  
Author(s):  
J. Kevin Vessey
Keyword(s):  
N2 Fixation ◽  
Cultivar Differences ◽  
Assimilate Partitioning ◽  
Fixation Rate

scholarly journals INVESTIGATING CULTIVAR DIFFERENCES IN STRESS-INDUCED ABSCISSION IN BELL PEPPER (CAPSICUM ANNUM L.) WITH GROWTH ANALYSIS

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 684a-684
Author(s):  
A.D. Turner ◽  
H.C. Wien
Keyword(s):  
Dry Matter ◽  
Growth Analysis ◽  
Bell Pepper ◽  
Cultivar Differences ◽  
Assimilate Partitioning ◽  
Dry Matter Partitioning ◽  
Capsicum Annum ◽  
Reproductive Structures ◽  
Flower Abscission

Cultivars of bell pepper differ in susceptibility to bud/flower abscission. Reduction in the level of assimilate, and alterations in assimilate partitioning may be involved in the processes leading to bud/flower abscission. Four growth analysis experiments were conducted to determine whether two pepper cultivars differing in susceptibility to stress-induced abscission showed corresponding differences in growth and rates and dry matter partitioning when subjected to shade stress. The reduction in RGR and NAR with shading was significantly greater for the abscission-susceptible `Shamrock' than the more tolerant `Ace'. Partitioning of dry matter to reproductive structures was reduced by shading. There were no cultivar differences in the proportion of dry matter partitioned to young developing leaves. Fully expanded leaves comprised a larger proportion of total dry matter in `Shamrock'. The lower NAR of `Shamrock' under stress may have led to greater bud/flower abscission than `Ace' under shade stress. If preferential partitioning of dry matter to competing structures (developing leaves) is also involved, it was not detected using this technique.

scholarly journals Determination of N2 and N2O Fixation Rates in Leguminous Plants and Three Different Soil Types by Labeling Experiments with Stable Nitrogen Isotopes

2018 ◽  
Author(s):  
Martin Nowak ◽  
Felix Koegler
Keyword(s):  
N2 Fixation ◽  
Root Nodules ◽  
Microbial Transformation ◽  
Terrestrial Ecosystems ◽  
Soil Types ◽  
Wetland Soils ◽  
N2o Emissions ◽  
Fixation Rate ◽  
Leguminous Plants ◽  
Uptake Rates

Nitrogen (N) is an essential nutrient and plays an important role in plant growth and physiology. In addition, N is also the limiting nutrient in most terrestrial ecosystems. The increasing use of N fertilizers increases agricultural production, but also has negative impacts on biodiversity, water quality and increases emissions of greenhouse gases such as nitrogen oxides (NOx) and nitrous oxide (N2O) into the atmosphere. N2O is a strong greenhouse gas and the product of microbial transformation processes of N introduced into soil and groundwater (nitrification and denitrification). The production of N2O in soils is highly dependent on oxygen and water content, soil temperature and texture and the available amount of reactive nitrogen (NO3- or NH4+). In agricultural soils, N2O emissions are also influenced by the type of fertilizer used, crops grown, soil pH and NO3- concentration. Refined forms of land management, such as the cultivation of legumes, can reduce the use of fertilizers and thus also the emission of N2O. Legumes can use symbiotic nodule bacteria (rhizobia) to bind atmospheric N2 and make it available to the plant. Non-symbiotic soil microorganisms such as cyanobacteria or other heterotrophic and autotrophic prokaryotes are also able to fix N2. Furthermore, the N2-fixing enzyme nitrogenase, which is specific for most organisms, is not specific for other N2 compounds, especially N2O. To study the N2 and N2O fixation potential of soils and legumes, experiments with isotope-enriched N-gases (100 mol% 15N2 and 15N2O) were performed. Three different soil types (forest, meadow and wetland) as well as legume plants inoculated with rhizobia bacteria (Rhizobium leucaneae) (Leucaena leucocephala) were incubated in microcosms with different mixing ratios of N2 and N2O over a period of one week. The measured 15N enrichment was then used to determine the biological uptake rates. Both in plants and in soils admixtures of up to 40% N2O had no influence on the N2 fixation rate. N2 uptake rates were 1.2 ± 0.4 ug N gdw-1 d- 1in forest and grassland soils and 3.9 ± 1.2 ug N gdw-1 d- 1 in wetland soils. In contrast, the N2 fixation rates of leguminous plants were significantly higher (130 ± 40 ug N gdw-1 d- 1), with the highest accumulation not in root nodules but in the roots. In both plants and soil, the N2O fixation of 0.2 ± 0.1 ug N gdw-1 d- 1 could only be measured from a concentration of 4 vol%. The results indicate that both soils and legumes have a high potential to bind atmospheric nitrogen in the form of both N2 but not N2O. The fate of nitrogen in soil needs to be further investigated. N2 fixation seems to play an important role in wetland soils. Legumes in particular have the potential for NH4+ input and N2O reduction, as most of the solid nitrogen has been transferred to the roots, which can contribute significantly to soil nutrient input.

scholarly journals Database of diazotrophs in global ocean: abundances, biomass and nitrogen fixation rates

2012 ◽  
Vol 5 (1) ◽  
pp. 47-106 ◽  
Author(s):  
Y.-W. Luo ◽  
S. C. Doney ◽  
L. A. Anderson ◽  
M. Benavides ◽  
A. Bode ◽  
...  
Keyword(s):  
N2 Fixation ◽  
Biomass Conversion ◽  
Geometric Mean ◽  
Deep Ocean ◽  
Global Ocean ◽  
Biological Fixation ◽  
Fixation Rate ◽  
Conversion Factors ◽  
Biogeochemical Models ◽  
Cell Counts

Abstract. Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Lower mean N2 fixation rate was found in the North Atlantic Ocean than the Pacific Ocean. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (53–73) Tg N yr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 4.7 (2.3–9.6) Tg C from cell counts and to 89 (40–200) Tg C from nifH-based abundances. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about ±70%. This evolving database can be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models. The database is stored in PANGAEA (http://doi.pangaea.de/10.1594/PANGAEA.774851).

scholarly journals Spatial variation in N<sub>2</sub>-fixation rate and diazotroph activity in the Tropical Atlantic

2007 ◽  
Vol 4 (3) ◽  
pp. 369-376 ◽  
Author(s):  
J. P. Montoya ◽  
M. Voss ◽  
D. G. Capone
Keyword(s):  
Water Column ◽  
N2 Fixation ◽  
Substantial Contribution ◽  
Tropical Atlantic ◽  
Full Data ◽  
Fixation Rate ◽  
Data Set ◽  
The North ◽  
Significant Difference

Abstract. A variety of N2-fixers occur in oligotrophic waters and these diazotrophs make a substantial contribution to the nitrogen budget of the upper water column. A synthesis of previously published and new rate measurements for the North Atlantic provides insight into the role of two different groups of N2-fixers (Trichodesmium and small diazotrophs) in supporting N2 fixation in the tropical Atlantic. The highest rates of N2 fixation occurred in the western part of the basin, but the full data set showed no significant difference between the eastern and western parts of the basin in overall rates of N2-fixation by the two groups of diazotrophs. N2-fixation by Trichodesmium was strongly dominant in the western part of the basin while small diazotrophs played a much larger role to the east of 40° W. The reasons for this shift in dominance are unclear, as is the identity of the small organisms fixing N2 in the water column.

Validity of N2 fixation rate measurements in marine Oscillatoria (Trichodesmium)

1987 ◽  
Vol 9 (6) ◽  
pp. 1047-1056 ◽  
Author(s):  
Edward J. Carpenter ◽  
Mary I. Scranton ◽  
Paul C. Novelli ◽  
Anthony Michaels
Keyword(s):  
N2 Fixation ◽  
Fixation Rate

scholarly journals Field effect of P fertilization on N2 fixation rate of Ulex europaeus

2007 ◽  
Vol 64 (8) ◽  
pp. 875-881 ◽  
Author(s):  
Xavier Cavard ◽  
Laurent Augusto ◽  
Etienne Saur ◽  
Pierre Trichet
Keyword(s):  
N2 Fixation ◽  
Field Effect ◽  
P Fertilization ◽  
Fixation Rate ◽  
Ulex Europaeus

Effects of Long-Term Fertilization Regimes on N2-Fixing Bacteria in a Luvisol Soil of Northeast China

2012 ◽  
Vol 599 ◽  
pp. 23-26
Author(s):  
Li Jia Cai ◽  
Yong Gang Xu ◽  
Wan Tai Yu
Keyword(s):  
Community Composition ◽  
N2 Fixation ◽  
Northeast China ◽  
Redundancy Analysis ◽  
N Availability ◽  
Community Structures ◽  
Free Living ◽  
Fixation Rate

Long-term fertilization significantly inhibited the free-living N2-fixation rate (FNR) mainly because of the increased NO3–-N. DGGE profiles and redundancy analysis (RDA) plots clearly revealed that long-term fertilizations changed the community structures of N2-fixing bacteria (NFB) due to differences in N availability and pH. In addition, the differences in community composition were correlated with the changes in process rates for NFB (P < 0.05).

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