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  • 1
    ISSN: 1438-3888
    Keywords: Key words Chondrus crispus ; Chlorophyll fluorescence ; Mastocarpus stellatus ; Mycosporine-like amino acids ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Chondrus crispus and Mastocarpus stellatus both inhabit the intertidal and upper sublittoral zone of Helgoland, but with C. crispus generally taking a lower position. Measurements of chlorophyll fluorescence, activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), and content and composition of UV absorbing mycosporine-like amino acids (MAAs) were conducted in the laboratory, to test whether susceptibility to UV radiation may play a role in the vertical distribution of these two species. Effective and maximal quantum yield of photochemistry as well as maximal electron transport rate (ETRmax) in C. crispus were more strongly affected by UV-B radiation than in M. stellatus. In both species, no negative effects of the respective radiation conditions were found on total activity of RubisCO. Total MAA content in M. stellatus was up to 6-fold higher than in C. crispus and the composition of MAAs in the two species was different. The results indicate that, among others, UV-B sensitivity may be a factor restricting C. crispus to the lower intertidal and upper sublittoral zone, whereas M. stellatus is better adapted to UV radiation and is therefore more competitive in the upper intertidal zone.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Protoplasma 111 (1982), S. 215-220 
    ISSN: 1615-6102
    Keywords: Osmotic stress ; Porphyra umbilicalis ; Rhodophyceae ; Thylakoid fine structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The fine structural organization of thylakoid membranes in intact cells ofPorphyra umbilicalis, an intertidal red alga, was studied using the freeze-fracture method with special emphasis on changes induced by hypo- and hyperosmotic stresses. In osmotically adapted plants the density of intramembraneous particles on the PF-face increases considerably in the osmotic range from 5-fold diluted to 6-fold concentrated artifical seawater medium ASP12, while that on the EF-face remains constant. The size of the particles on both fracture faces decreases strongly from extreme hypoosmotic to extreme hyperosmotic stress. These findings are discussed with relation to their biological significance.
    Type of Medium: Electronic Resource
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