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  • 1
    Electronic Resource
    Electronic Resource
    Development of the photosynthetic apparatus during light-dependent greening of a mutant of Chlorella fusca (1978)
    Springer
    Planta 140 (1978), S. 45-52 
    Details
    ISSN: 1432-2048
    Keywords: Cytochrome f ; Development photosynthetic apparatus ; Greening mutant ; Photochemical activities ; Photosynthetic unit ; P-700 ; Ribulose bisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The formation of chlorophyll, cytochrome f, P-700, ribulose bisphosphate carboxylase as well as photosynthesis and Hill reaction activities were tested during the light-dependent greening process of the Chlorella fusca mutant G 10. Neither chlorophyll nor protochlorophyllide was detected in the darkgrown cells. When transferred to light the mutant cells developed chlorophyll and established its photosynthetic capacity after a short lag phase. In the in vivo absorption spectra a spectral shift of the red absorption peak position from 674 to 680 nm was indicated during the first 3 h of greening. Cytochrome f was already present in the dark-grown cells, but during the greening phase a threefold increase in the cytochrome f content could be seen. At the early stages of greening a characteristic primary oscillation in the content of cytochrome f was observed. P-700 was lacking in the dark and during the first 30 min of illumination. From the first to the second h of light a forced synthesis of P-700 took place and the time-course curve for the ratios of P-700/chlorophyll rose to a sharp maximum. The synthesis of P-700 started together with photosystem I activity and showed similar kinetics. We found the simultaneous appearance of photosystem II, photosystem I, and photosynthetic activities 30 min after the beginning of the illumination. Based on chlorophyll content they attained maximum activity after 2 h of light, but at this time photosystem I capacity proved to be remarkably higher than photosynthetic and photosystem II activities. Highest carboxylase activity existed in darkgrown cells. During the greening process the activity of the enzyme decreased continuously. After 2 h of illumination chlorophyll synthesis partially served to increase the size of the photosynthetic unit, which consequently led to a decrease in the light energy needed to saturate photosynthesis and also to a decrease of photosynthetic rate based on chlorophyll content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389378
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  • 2
    Electronic Resource
    Electronic Resource
    Measurements of cytochrome f and P-700 in intact leaves of Sinapis alba grown under high-light and low-light conditions (1979)
    Springer
    Planta 146 (1979), S. 377-385 
    Details
    ISSN: 1432-2048
    Keywords: Cytochrome f ; Electron-transport ; High-light plants ; Low-light plants ; P-700 ; Photosynthetic unit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The oxidation and reduction of cytochrome f and P-700 is measured spectrophotometrically in leaves of low-light and high-light plants. After illumination with red light, an induction phenomenon for cytochrome f oxidation is observed which indicates a regulation of photosystem I activity through energy distribution between the pigment systems by the energy state of the membrane. After far-red excitation the reduction of cytochrome f in the dark is much slower in low-light leaves. This shows that cyclic electron transport is not improved in low-light plants under these conditions. P-700 is oxidized on excitation with far-red light. However, with high intensities of far-red light, P-700 is partially reduced again which is due to a low extent of photosystem II excitation with the far-red used in the experiments. The low-light leaves show greater sensitivity of photosystem II to this excitation. The initial rate of the cytochrome f oxidation-rate is the same in low-light and high-light leaves. This shows that several P-700 are connected with only one electron transport chain. The consequences of these results concerning the tripartite concept and the photosynthetic unit are discussed. In the high-light plants the experimental data can be well explained by the tripartite organization of the photosynthetic unit. In low-light plants, however, a multipartite organization has to be postulated. In the partition regions of the grana, several antennae systems I, antennae systems II, and light-harvesting complexes can communicate with one electron transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00380848
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  • 3
    Electronic Resource
    Electronic Resource
    The intensification of absorbance changes in leaves by light-dispersion (1979)
    Springer
    Planta 146 (1979), S. 551-557 
    Details
    ISSN: 1432-2048
    Keywords: Cytochrome f ; High-light plants ; Low-light plants ; Light-dispersion ; P-700
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In dispersive samples, like leaves, the absorbance of pigments is intensified. The intensification is due to a longer optical path through the dispersive sample. However, in chloroplast suspensions the optical path is not much longer than in clear solutions. The factor of intensification β (=the lengthening of the optical path) is calculated by comparing the absorbance of leaves and the absorbance of chloroplast suspensions with equal pigment-content. This method also includes the influence of possible sieve effects which could decrease absorbance. The measurements are carried out with high- and low-light leaves of different thickness and pigment content. The intensification of absorbance was 2–2.5 fold. In highlight leaves it was somewhat less than in low-light leaves. The factor β is better correlated to the pigment content than to the thickness of the leaves. The plot of absorbance versus the pigment content of the leaves shows that β decreases with increasing pigment content. In contrast, chloroplast suspensions show a linear dependence as expected from Lambert-Beer's law. Thus, in leaves with very low pigment content the absorbance is intensified up to 6 fold while the intensification decreases with increasing absorbance. These results are in good agreement with measurements of Tsel'niker (1975) and with the theoretical predictions of Butler's formula (1960). Absorbance changes due to photooxidation of P-700 and cytochrome f in intact leaves are measured, and β is used to calculate the amount of the oxidized components. Without correction for β the values would be much greater than the amount actually present. The corrected data show that between 70 and 90% of the present P-700 and cytochrome f can be photooxidized in the intact leaf.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388831
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of mild drying on the mineralization of soil nitrogen (1985)
    Springer
    Plant and soil 84 (1985), S. 175-179 
    Details
    ISSN: 1573-5036
    Keywords: Biomas ; Drying ; Mineralization ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Drying soil to −100 kPa increased the subsequent mineralization of nitrogen under optimal moisture conditions. The effect was greater when the soils were dried to −1500 Pa. Mineralization was greater after four cycles of wetting and drying than after one. Depending on the drying conditions, the amount of nitrogen mineralized after drying to −1500 Pa was between 6.8 and 18.2% of that mineralized after chloroform fumigation. After drying the soils the average ratio of ΔCO2-C respired to Δmin N was 21.1–22.3 depending on the drying conditions, whereas after chloroform treatment and autoclaving the ratio was 6.0 and 9.9 respectively. The effect of drying on nitrogen mineralization is attributed to two causes: the death and subsequent lysis of a small proportion of the soil organisms, and to the desorption of organic substances with a wide C/N ratio. Because of the stimulation of even mild drying conditions, marked differences in mineralization rates of soil nitrogen between cropping seasons must be expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02143181
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    Paper (German National Licenses)
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