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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 101 (1994), S. 0 
    ISSN: 1471-0528
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1520-5827
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract. The effect of growth temperatures on quantum yield (φ) was examined for leaves at different stages of development within the immature canopies of two crops of field grown maize (Zea mays cv. LG11) sown on 3 May and 20 June 1990. During the period of 23 to 49d after sowing, the crop sown on the 3 May experienced temperatures below 10°C on 19 occasions compared with only two for the crop sown on 20 June. A period of severe chilling at the end of May and the beginning of June was associated with a marked reduction in φ for all leaves in the early-sown crop. This chill-induced depression in φ was greater in recently emerged than more mature leaves in the canopy and was found to be accompanied by modifications in the polypeptide profiles of thylakoids isolated from the leaves. During the chilling period, decreases in some polypeptides, notably in the range of 41–42 and 20kDa apparent molecular size, and increases of polypeptides of c. 15–16kDa were observed compared with leaves developing at warmer temperatures in July. The efficiency of converting intercepted radiation into dry matter (conversion efficiency) was 42% lower in the early- than late-sown crop, but no significant relationship between conversion efficiency and quantum yield was found in either treatment.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 106 (1999), S. 0 
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Six genotypes of Zea mays L. were grown in pots inside a glasshouse at a mean temperature of 22±2°C and a minimum photosynthetic photon flux density (Q) during the daylight period of 400 μmol m−2 s−1. Chilling-dependent photoinhibition was induced by exposing plants to a temperature of 7°C and a Q of 1 000 μmol m−2 s−1 for 6 h. Recovery from photoinhibition was then followed at a temperature of 25°C and a Q of 200 μmol m−2 s−1. Leaf gas exchange and chlorophyll fluorescence were measured on attached leaves at room temperature prior to the photoinhibitory treatments and at 6 sampling intervals from 0 to 24 h during the recovery period. The relative water content (RWC) was also measured during the recovery period. The results showed a significant genotypic variation in the susceptibility to and rate of recovery from chilling-dependent photoinhibition of photosynthesis in Zea mays seedlings. The Highland Pool 1a from highland sites in Mexico was the least susceptible to chill-induced photoinhibition, but had the slowest rate of recovery. The hybrid variety LG11 showed the highest rate of recovery, whilst the inbred line ZPF307 was the most susceptible to chill-induced photoinhibition. Susceptibility to photoinhibition and subsequent recovery were at least partially independent, suggesting that selection for improved genotypes will require independent selection for both tolerance and capacity for recovery. Although chlorophyll fluorescence provided a more rapid method of assessing the occurrence of photoinhibition, it was not as effective as direct gas-exchange measurements of the maximum quantum yield of photosynthesis (φ) in separating genotypes with respect to their susceptibility to photoinhibition, especially in the most vulnerable genotypes such as ZPF307. Water stress induced by chilling and high Q treatments appeared to impair the recovery processes. Decreases in stomatal conductance (gs) produce a significant decrease in intercellular CO2 concentration (Ci), although this decrease was never so extreme that it limited photosynthetic rates at the light intensities used to determine φ. Nevertheless, closure of stomata in patches, producing local restriction of CO2 supply, would explain the poor correlation between chlorophyll fluorescence and quantum yield measurements in some genotypes immediately after photoinhibitory treatments.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1600-5759
    Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    The @International Journal Of Applied Radiation And Isotopes 22 (1971), S. 627-629 
    ISSN: 0020-708X
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Energietechnik , Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 31 (1986), S. 201-204 
    ISSN: 1432-1041
    Schlagwort(e): hyperlipidaemia ; acipimox ; adverse effects ; plasma glucose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Fifty-two patients with Fredrickson Type IIb or Type IV hyperlipidaemia, in whom diet had not achieved satisfactory lipid levels, completed a double blind randomised study of acipimox versus placebo. The patients were given acipimox, 250 mg three times daily or placebo for a three month period, and plasma lipids and glucose were monitored. The patients receiving acipimox showed a fall in the mean concentration of plasma triglyceride compared to placebo (0.74 mmol/l) and this was most marked in patients whose initial plasma triglyceride levels were greater than 3 mmol/l (1.0 mmol/l, confidence limits 0.18, 1.82). Acipimox was well tolerated, and could be a useful addition to the drugs available for the treatment of patients with hypertriglyceridaemia.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 214 (1988), S. 80-84 
    ISSN: 1617-4623
    Schlagwort(e): ColE1 ; Plasmid stability ; Site-specific recombination ; Multimerisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The heritable stability of the multicopy plasmid ColE1 and its natural relatives, requires the presence in the plasmid of a site (cer in ColE1) that acts as a substrate for site-specific recombination, thereby maintaining plasmids in the monomeric state. Multimerization, promoted by homologous recombination, leads to plasmid loss. Here we show that the Escherichia coli chromosome encodes at least two unlinked functions that act on cer and its analogous sites, to promote stabilizing site-specific recombination. One of these functions is encoded by a gene residing on a cosmid that also contains the argI and pyrB genes, mapping it to the 96–97 min region of the E. coli map.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1573-5079
    Schlagwort(e): chilling ; photosynthesis ; crop radiation-use efficiency ; maize
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of growth temperatures on the photosynthetic performance of field grown maize (Zea mays cv. LG11) was examined for crops sown on 1 May and 28 June 1991. During the period of growth, 2 May to 10 August, the early-sown crop experienced temperatures below 10 °C on 33 occasions compared with only one for the crop sown on 28 June. The prolonged period of low temperatures throughout May and beginning of June were associated with a marked depression in CO2 assimilation rates at all light levels in the early-sown treatment. Chill-induced depression of the photosynthetic light-response curve reflected a sustained reduction in canopy leaf photosynthesis and crop radiation-use efficiency (RUE). During the early stages of growth, RUE was 65% lower in the early- than late-sown treatment, with no marked recovery observed in the former treatment until approximately three weeks after chilling conditions had ceased. Data show a close correlation between chill-induced depression of quantum yield (Φ) and RUE, with corresponding reductions in the light-saturated rates of CO2 assimilation (Pmax). The convexity of the light-response curve recovered most rapidly from chilling temperatures, and at least three weeks before any improvement in RUE. It is concluded that photosynthetic productivity of immature maize stands is less sensitive to changes in the convexity of the light response, than to changes in either Φ or Pmax.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; leaf age ; maize
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Changes in the photosynthetic light-response curve during leaf development were determined for the fourth leaf of maize crops sown on 23 April and 10 June. Temperatures were unusually mild during late spring/early summer and neither crop experienced chilling damage. The concept of thermal time was used to take into account the effects of different temperature regimes on developmental stage, thereby enabling photosynthetic light-response data to be combined for both crops to describe the general response. Large variations in the upper asymptote (Asat) and convexity (Θ) of the light-response curve occurred during leaf development, but the maximum quantum yield of CO2 assimilation remained relatively constant throughout. Dark respiration rates showed a small but significant decrease with leaf age and generally ranged between 5 and 10% of Asat. A simple mathematical model was developed to assess the sensitivity of daily leaf photosynthesis (AL) to reductions in the Asat, Θ and the initial slope (Φ) of the light-response curve at different stages of leaf development. On bright sunny days, and at all developmental stages, AL was ca. twice as sensitive to reductions in Asat than to reductions in Φ and Θ. In overcast conditions, however, all three parameters contributed significantly to reductions in leaf photosynthesis, although the contribution of Φ was greatest during early leaf growth, while older leaves were most sensitive to depressions in Asat. The implications of these results for modelling the sensitivity of canopy photosynthesis to chill-induced photoinhibition of the light-response curve are discussed.
    Materialart: Digitale Medien
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