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  • Doubly labelled water  (3)
  • Fire intensity  (3)
  • Nitrogen fixation  (3)
  • Springer  (9)
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  • 1
    ISSN: 1432-1939
    Keywords: Doubly labelled water ; Energy expenditure ; Metabolism ; Sexual selection ; Tail ornament
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Different hypotheses stress the importance of natural or sexual selection to explain the evolution and maintenance of long outermost tail feathers in the barn swallow (Hirundo rustica). Since energy costs are predicted to arise from tail length manipulation, we measured the daily energy expenditure in three experimental groups (tail-shortened, tail-elongated, and control birds) with the doubly labelled water technique. Though we did not directly measure flight cost, we assumed this to be positively related to daily energy expenditure. Mass independent daily energy expenditure (kJ/mass0.67 day) average daily metabolic rate (ml CO2/g h), and water flux (ml H2O/g day) did not show any significant difference among treatments in either sex. Males had higher values than females for the three parameters. Males with short original tail length experienced a higher water flux than originally long-tailed males. Females that laid more eggs during the breeding season or had heavier broods also showed higher levels of water flux which could imply a higher food intake. Our expectation of finding energetic costs of manipulated tail length in barn swallows with an integrated measure of metabolism was not fulfilled, and we did not find evidence for behavioural changes in the birds involved in the experiment.
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  • 2
    ISSN: 1432-1939
    Keywords: Key words Daily energy expenditure ; Doubly labelled water ; Parental effort ; Parus major ; Working day length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The variation in time and energy allocation of female great tits, Parus major, was studied in five different European populations across a latitudinal gradient. Daily energy expenditure (DEE) was measured in females tending 12-day-old broods. The number of daylight hours used by the parents to collect food for the brood increased with latitude, while DEE and feeding rate per brood tended to level off with latitude. Individual variation in DEE could be explained by variation in ambient temperature (–), the duration of activity period (+) and area, but not by brood size, female body mass, brood mass or feeding rate. When the effect of ambient temperature and the duration of the activity period on the day of energy expenditure measurements were controlled for, female DEE still tended to level off with latitude. Temperature and activity alone can thus not explain the observed pattern. The present study suggests that parents at southern latitudes may be under a time constraint and do not increase energy expenditure because they have no more daylight hours available for foraging, while birds at northern latitudes may be under an energy constraint because they do not make full use of the long daylight period available.
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  • 3
    ISSN: 1432-1939
    Keywords: Delichon urbica ; Doubly labelled water ; House martin ; Oeciacus hirundinis ; Parasite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We measured the energy cost of ectoparasitism in an experimental study of the house martin bug Oeciacus hirundinis and its main host, nestlings of the house martin Delichon urbica. Nests were randomly assigned to inoculation with 0 (control) 10, or 100 bugs during egg laying, and this resulted in statistically significant differences in parasite loads following fledging of nestlings. Parasite loads negatively affected house martin nestlings as estimated from their body mass at age 16 days and from mass loss estimated over 1 day late in the nestling period. Daily energy expenditure (KJ/d), average daily metabolic rate (ml CO2/g h), and mass independent daily energy expenditure (kJ/mass0.67d) did not differ significantly between experimental treatments. However, average daily metabolic rate increased with increasing intensities of ectoparasitism. Mass independent daily energy expenditure also increased with higher levels of parasite infestation. These results demonstrate that the bug imposes an energy cost on its host by elevating the level of metabolism.
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  • 4
    ISSN: 1432-1939
    Keywords: Fire intensity ; Adenostoma fasciculatum ; Lignotuber ; Resprouting ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in the population structure of the lignotuberous resprouter Adenostoma fasciculatum were investigated by experimentally burning at various intensities an old stand in southern California chaparral. Survival after fire, time of resprouting, herbivory, and survival after resprouting were monitored for more than 1 year after the fire. Greater fire intensity increased plant mortality and the size of plants that died as a consequence of the fire. Time from the fire until resprouting increased with increasing fire intensity and was related to plant size: the larger the plants the earlier they resprouted. Post-resprouting mortality also increased with fire intensity and was related to time of resprouting. Herbivory increased with fire intensity and the size of plants affected by it changed with the intensity of the fire. Fire intensity had profound direct and indirect effects on the population structure of Adenostoma fasciculatum. Plant size strongly determined the direct and indirect lethal effects of fire.
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  • 5
    ISSN: 1432-1939
    Keywords: Adenostoma fasciculatum ; California chaparral ; Fire intensity ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Resprouting is the main regeneration mechanism after fire in Mediterranean-type ecosystems. Herbivores play an important role in controlling postfire seedling establishment, but their influence on regeneration by resprouting is less well known. To study the effects of fire intensity on resprouting of Adenostoma fasciculatum in southern California chaparral, and its interaction with herbivory, we conducted an experimental burn at three levels of fire intensity. We found that increasing fire intensity increased plant mortality, reduced the number of resprouts per plant, and delayed the time of resprouting. Herbivory increased with fire intensity, and was related to the time of resprouting. Plants resprouting later in the season and out of synchrony with the main flush were attacked more readily by herbivores. Post-resprouting mortality also increased with fire intensity and was significantly associated with herbivory in the higher fire intensity plots. Fire intensity effects on chaparral regeneration by resprouting may be farreaching through effects on the population structure, resprout production, and growth of Adenostoma fasciculatum.
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  • 6
    ISSN: 1617-4623
    Keywords: Rhodobacter capsulatus ; Nitrogen fixation ; DNA sequence analysis ; nifE, nifN, nifX genes ; Protein comparisons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Rhodobacter capsulatus genes homologous to Klebsiella pneumoniae nifE, nifN and nifX were identified by DNA sequence analysis of a 4282 bp fragment of nif region A. Four open reading frames coding for a 51188 (NifE), a 49459 (NifN), a 17459 (NifX) and a 17472 (ORF4) dalton protein were detected. A typical NifA activated consensus promoter and two imperfect putative NifA binding sites were located in the 377 bp sequence in front of the nifE coding region. Comparison of the deduced amino acid sequences of R. capsulatus NifE and NifN revealed homologies not only to analogous gene products of other organisms but also to the α and β subunits of the nitrogenase iron-molybdenum protein. In addition, the R. capsulatus nifE and nifN proteins shared considerable homology with each other. The map position of nifX downstream of nifEN corresponded in R. capsulatus and K. pneumoniae and the deduced molecular weights of both proteins were nearly identical. Nevertheless, R. capsulatus NifX was more related to the C-terminal end of NifY from K. pneumoniae than to NifX. A small domain of approximately 33 amino acid residues showing the highest degree of homology between NifY and NifX was also present in all nifB proteins analyzed so far. This homology indicated an evolutionary relationship of nifX, nifY and nifB and also suggested that NifX and NifY might play a role in maturation and/or stability of the iron-molybdenum cofactor. The open reading rame (ORF4) downstream of nifX in R. capsulatus is also present in Azotobacter vinelandii but not in K. pneumoniae. Interposon-induced insertion and deletion mutants proved that nifE and nifN were necessary for nitrogen fixation in R. capsulatus. In contrast, no essential role could be demonstrated for nifX and ORF4 whereas at least one gene downstream of ORF4 appeared to be important for nitrogen fixation.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 139 (1998), S. 91-101 
    ISSN: 1573-5052
    Keywords: Cytisus sp. ; Fire behavior ; Fire intensity ; Fire severity ; Heat output per unit area ; Mediterranean-type shrublands ; Minimum branch diameter ; Open-calorimeters ; Pyrometers ; Spain ; Temperature-residence-time
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methods are presented to relate temperature-residence-time at the soil surface, i.e., time above 150 ºC as an estimation of the severity of a fire, with measurements made during an experimental fire or on two post hoc measurements. The experiment was carried out in a shrubland dominated by the woody-legume Cytisus striatus subsp. eriocarpus, in Central Spain. Temperature-sensitive paints, and steam-releasing open-calorimeters were used as fire-meters during the burn. Post hoc measurements used were estimations of heat output per unit area, and measurements of the minimum diameter of branches of Cytisus remaining after the fire. Time above 150 ºC was obtained from measurements made with thermocouples placed at the soil surface in 20 contiguous 1×1 m squares of the burn plot. All other measurements were made at each 1×1 m in the 22×3 m rectangle surrounding, and including, the thermocouple squares. Various simple and multiple regression models were constructed to predict time above 150 ºC from each of the four measurements made during or after the fire. Maximum coefficients of determination obtained for regressions were 0.61 and 0.62 for water mass loss from open-calorimeters and branch diameter, respectively. Using all the variables in a multiple regression model, time above 150 ºC was related to water mass loss from open-calorimeters and heat output per unit area with a coefficient of determination of 0.77. It is concluded that estimations of time above 150 ºC at the soil surface during the passage of fire may be possible based on simple devices, such as open-calorimeters, or on biological indicators, such as minimum branch diameters. Additionally, combining two methods (open-calorimeters, estimations of heat output per unit area) may allow the reconstruction of the time above 150 ºC during the fire at a scale of 1 2, an important characteristic of a burn to understand ecosystem response to fire.
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  • 8
    ISSN: 1617-4623
    Keywords: Nitrogen fixation ; Novel type of NifU ; Ethane formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract DNA sequence analysis of a 3494-bp HindIII-Bc1I fragment of the Rhodobacter capsulatus nif region A revealed genes that are homologous to ORF6, nifU, nifS, nifV and nifW from Azotobacter vinelandii and Klebsiella pneumoniae. R. capsulatus nifU, which is present in two copies, encodes a novel type of NifU protein. The deduced amino acid sequences of NifUI and NifUII share homology only with the C-terminal domain of NifU from A. vinelandii and K. pneurnoniae. In contrast to nifA andnifB which are almost perfectly duplicated, the predicted amino acid sequences of the two NifU proteins showed only 39% sequence identity. Expression of the ORF6-nifU ISVW operon, which is preceded by a putative σ54-dependent promoter, required the function of NifA and the nif-specific rpoN gene product encoded by nifR4. Analysis of defined insertion and deletion mutants demonstrated that only nifS was absolutely essential for nitrogen fixation in R. capsulatus. Strains carrying mutations in nifV were capable of very slow diazotrophic growth, whereas ORF6, nifU I and nifW mutants as well as a nifU I/nifUII, double mutant exhibited a Nif+ phenotype. Interestingly, R. capsulatus nifV mutants were able to reduce acetylene not only to ethylene but also to ethane under conditions preventing the expression of the alternative nitrogenase system. Homocitrate added to the growth medium repressed ethane formation and cured the NifV phenotype in R. capsulatus. Higher concentrations of homocitrate were necessary to complement the NifV phenotype of a polar nifV mutant (NifV−NifW−), indicating a possible role of NifW either in homocitrate transport or in the incorporation of this compound into the iron-molybdenum cofactor of nitrogenase.
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  • 9
    ISSN: 1573-5079
    Keywords: Anabaena ; ferredoxin ; flavodoxin ; FPLC determination of ferredoxin and flavodoxin ; Iron deficiency ; Nitrogen fixation ; Photosynthesis ; strain differences in gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Iron-dependent formation of ferredoxin and flavodoxin was determined in Anabaena ATCC 29413 and ATCC 29211 by a FPLC procedure. In the first species ferredoxin is replaced by flavodoxin at low iron levels in the vegetative cells only. In the heterocysts from Anabaena ATCC 29151, however, flavodoxin is constitutively formed regardless of the iron supply. Replacement of ferredoxin by flavodoxin had no effect on photosynthetic electron transport, whereas nitrogen fixation was decreased under low iron conditions. As ferredoxin and flavodoxin exhibited the same Km values as electron donors to nitrogenase, an iron-limited synthesis of active nitrogenase was assumed as the reason for inhibited nitrogen fixation. Anabaena ATCC 29211 generally lacks the potential to synthesize flavodoxin. Under iron-starvation conditions, ferredoxin synthesis is limited, with a negative effect on photosynthetic oxygen evolution.
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