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'Senescence' in keywords Facet   section ZfN Section C  [X]
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1Author    H. K. KleudgenRequires cookie*
 Title    Veränderungen der Pigment-und Prenylchinongehalte in Chloroplasten von Gerstenkeimlingen nach Applikation des Wuchsstoffherbizids MCPA (4-Chlor-2-methylphenoxyessigsäure) Changes of the Amounts of Pigments and Prenylquinones in Chloroplasts of H ordeum vulgare — Seedlings Treated with the Growth Regulating Herbicide MCPA (4-Chloro-2-methylphenoxyacetic Acid)  
 Abstract    MCPA (4-chloro-2-methylphenoxyacetic acid) was applied (1, 10, 100 ^ m/ 1) via the roots to 4 day old etiolated barley seedlings, which were subjected to continuous white light at the same time. The prenyllipids of chloroplasts (chlorophylls, carotenoids, prenylquinones) were determined 7 and 10 days after sowing. Chlorophyll accumulation was reduced by up to 40% compared to the control depending on the herbicide concentration. The formation of carotenoids was inhibited to a lower degree, the ratio xanthophylls/carotenes being increased. There were decreasing ratios of chlorophyll a/benzoquinones and a higher inhibition of the oxidized benzoquinones plastoquinone-9 and a-tocoquinone compared to the reduced forms plastohydroquinone-9 and a-tocopherol. Very similar changes had been observed in earlier works on barley seedlings undergoing an artificial degeneration of their chloroplasts in the dark. It is suggested that MCPA induces a state of senescence in the prenyllipid metabolism of the photosynthetic apparatus, which is cor­ related with respect to structure, to a reduction of the pigment antennae. 
  Reference    Z. Naturforsch. 34c, 106 (1979); eingegangen am 13. November 1978 
  Published    1979 
  Keywords    Growth-Regulator, Prenyllipids, Chloroplasts, Senescence 
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 TEI-XML for    default:Reihe_C/34/ZNC-1979-34c-0106.pdf 
 Identifier    ZNC-1979-34c-0106 
 Volume    34 
2Author    H.Oskar SchmidtRequires cookie*
 Title    The Structure and Function of Grana-Free Thylakoid Membranes in Gerontoplasts of Senescent Leaves of Vicia faba L  
 Abstract    In the course of yellowing (senescence) the leaves of Vicia faba L. lose 95% of their chlorophyll. Gerontoplasts develop from chloroplasts and aggregate with the pycnotic mitochon-dria and the cell nucleus in the senescent cells (organelle aggregation). The gerontoplasts contain only a few, unstacked thylakoid membranes but a large number of carotinoid-containing plasto-globuli, which after the degration of chlorophyll presumably assume the light protection of the cells. The thylakoid membranes of the gerontoplasts were isolated by means of a flotation method. Their polypeptide composition is characterized by a high proportion of light-harvesting complex. Evidence of relatively high photochemical activity shows that functional thylakoid mem-branes are present in the premortal senescence state of leaves and this suggests that there is functional compartmentation of the hydrolytic processes in this stage of the leaves' development. 
  Reference    Z. Naturforsch. 43c, 149—154 (1988); received March 11/September 7 1987 
  Published    1988 
  Keywords    Senescence, Chloroplast, Gerontoplast, Thylakoid Membrane Proteins, Electronmicroscopy, Photosynthesis 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0149.pdf 
 Identifier    ZNC-1988-43c-0149 
 Volume    43 
3Author    Agnieszka MostowskaRequires cookie*
 Title    Response of Chloroplast Structure to Photodynamic Herbicides and High Oxygen  
 Abstract    Response of chloroplast on the structural level to photodynamic herbicides and high oxy­ gen concentration was compared with symptoms of chloroplast senescence. Based on the present results and those known from the literature a general pattern of response was pro­ posed: the action of most of environmental factors induces the oxidative stress and often gives similar symptoms of structural damage and dysfunctions independent of the primary stressing factor. These alterations consist mostly in swelling of thylakoids, disruption of chlo­ roplast membranes, intensive plastoglobuli accumulation, photodestruction of pigments and inhibition of photosynthesis. 
  Reference    Z. Naturforsch. 54c, 621 (1999); received November 4 1998/February 18 1999 
  Published    1999 
  Keywords    Chloroplast Ultrastructure, Environmental Factors, Oxidative Stress Photodynamic Herbi­ cides, Senescence 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0621.pdf 
 Identifier    ZNC-1999-54c-0621 
 Volume    54