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  • Photosynthesis
  • Springer  (3)
  • American Geophysical Union
  • PANGAEA
  • 1975-1979  (3)
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  • Springer  (3)
  • American Geophysical Union
  • PANGAEA
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Year
  • 1
    ISSN: 1432-2048
    Keywords: C3-plants ; CO2 and photorespiration ; Helianthus ; Photorespiration ; Photosynthesis ; Temperature and photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using an open gas-exchange system, apparent photosynthesis, true photosynthesis (TPS), photorespiration (PR) and dark respiration of sunflower (Helianthus annuus L.) leaves were determined at three temperatures and between 50 and 400 μl/l external CO2. The ratio of PR/TPS and the solubility ratio of O2/CO2 in the intercellular spaces both decreased with increasing CO2. The rate of PR was not affected by the CO2 concentration in the leaves and was independent of the solubility ratio of oxygen and CO2 in the leaf cell. At photosynthesis-limiting concentrations of CO2, the ratio of PR/TPS significantly increased from 18 to 30°C and the rate of PR increased from 4.3 mg CO2 dm-2 h-1 at 18°C to 8.6 mg CO2 dm-2 h-1 at 30°C. The specific activity of photorespired CO2 was CO2-dependent but temperature-independent, and the carbon traversing the glycolate pathway appeared to be derived both from recently fixed assimilate and from older reserve materials. It is concluded that PR as a percentage of TPS is affected by the concentrations of O2 and CO2 around the photosynthesizing cells, but the rate of PR may also be controlled by other factors.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Photosynthesis ; Blue-Green Alga ; Phormidium sp. ; Oxidation-Reduction Potential ; Sulfide ; Hot Spring ; Stronatolite ; Anaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis in a Phormidium species which forms dense conical-shaped structures in thermal springs is strongly inhibited by aeration but is stimulated by sulfide and other agents (cysteine, thioglycolate, sulfite) which lower the oxidation-reduction potential. The compact structures which this alga forms in nature may restrict oxygen penetration from the environment so that the anaerobic or microaerophilic conditions necessary for photosynthesis can develop. The alga may be defective in a regulatory mechanism that controls the reoxidation of reduced pyridine nucleotides formed during photosynthesis. It is suggested that other mat-forming and benthic blue-green algae may also prefer anaerobic conditions for growth and photosynthesis.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: Chloris ; Humidity ; Nitrogen ; Nutrition ; Photosynthesis ; Rhodes grass ; Salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Under high atmospheric humidity, Rhodes grass plants responded favourably to an increase in nitrate fertilization. Under low atmospheric humidity an optimum point was reached at lower N-treatment. Plants' growth was improved by a salinity treatment of up to 100 mM, at high atmospheric humidity. A higher salt concentration cancelled the favourable effect of added nitrate. The rise in yield which follows salt or nitrate treatments is apparently combined with an increase in activity of the key photosynthetic enzymes, Phosphoenol pyruvate carboxylase and Ribulose biphosphate carboxylase. A similar rise in activity is seen in nitrate reductase, a key enzyme in nitrogen metabolism. Evidently, all three enzymatic systems are not damaged in high salt treatments, and the potential photosynthetic capacity remained practically uneffected in all treatments. As no correlation could be found between transpiration and growth curves, it is assumed that the supply of CO2 is also unhampered. Thus, the major negative effect of salinity, seems to be on protein synthesis, which eventually leads to disturbed growth.
    Type of Medium: Electronic Resource
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