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  • 1
    Digitale Medien
    Digitale Medien
    Sensitivity of Laminariales zoospores from Helgoland (North Sea) to ultraviolet and photosynthetically active radiation: implications for depth distribution and seasonal reproduction (2005)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 28 (2005), S. 0 
    Details
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Depth distribution of kelp species in Helgoland (North Sea) is characterized by occurrence of Laminaria digitata in the upper sublittoral, whereas L. saccharina and L. hyperborea dominate the mid and lower sublittoral region. Laminaria digitata is fertile in summer whereas both other species are fertile in autumn/winter. To determine the light sensitivity of the propagules, zoospores of L. digitata, L. saccharina and L. hyperborea were exposed in the laboratory to different exposure times of photosynthetically active radiation (PAR; 400–700 nm), PAR + UVA radiation (UVAR; 320–400 nm) and PAR + UVAR + UVB radiation (UVBR; 280–320 nm). Optimum quantum yield of PSII and DNA damage were measured after exposure. Subsequently, recovery of photosynthetic efficiency and DNA damage repair, as well as germination rate were measured after 2 and 3 d cultivation in dim white light. Photosynthetic efficiency of all species was photoinhibited already at 20 µmol photons m−2 s−1 PAR, whereas UV radiation (UVR) had a significant additional effect on photoinhibition. Recovery of the PSII function was observed in all species but not in spores exposed to irradiation longer than 4 h of PAR + UVA + UVB and 8 h of PAR + UVA. The amount of UVB-induced DNA damage measured as cyclobutane–pyrimidine dimers (CPDs) increased with exposure time and highest damage was detected in the spores of lower subtidal L. hyperborea relative to the other two species. Significant removal of CPDs indicating repair of DNA damage was observed in all species after 2 d in low white light especially in the spores of upper subtidal L. digitata. Therefore, efficient DNA damage repair and recovery of PSII damage contributed to the germination success but not in spores exposed to 16 h of UVBR. UV absorption of zoospore suspension in L. digitata is based both on the absorption by the zoospores itself as well as by exudates in the medium. In contrast, the absorption of the zoospore suspension in L. saccharina and L. hyperborea is based predominantly on the absorption by the exudates in the medium. This study indicates that UVR sensitivity of zoospores is related to the seasonal zoospore production as well as the vertical distribution pattern of the large sporophytes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-3040.2005.01288.x
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  • 2
    Digitale Medien
    Digitale Medien
    Action spectrum of phaeoplast displacements from the dark to the low intensity arrangement in the brown alga Dictyota dichotoma
    Amsterdam : Elsevier
    Journal of Photochemistry and Photobiology B: Biology 4 (1989), S. 111-121 
    Details
    ISSN: 1011-1344
    Schlagwort(e): Dictyota ; action spectrum ; chloroplast movements ; photoreceptor.
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/1011-1344(89)80106-X
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  • 3
    Digitale Medien
    Digitale Medien
    Photosynthetic characteristics and mycosporine-like amino acids under UV radiation: a competitive advantage of Mastocarpus stellatus over Chondrus crispus at the Helgoland shoreline? (2000)
    Springer
    Helgoland marine research 54 (2000), S. 47-52 
    Details
    ISSN: 1438-3888
    Schlagwort(e): Key words Chondrus crispus ; Chlorophyll fluorescence ; Mastocarpus stellatus ; Mycosporine-like amino acids ; UV radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s101520050035
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  • 4
    Digitale Medien
    Digitale Medien
    Capability of dynamic photoinhibition in Arctic macroalgae is related to their depth distribution (1998)
    Springer
    Marine biology 131 (1998), S. 361-369 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The capability of several macroalgal species to protect photosynthesis from excessive irradiance by dynamic photoinhibition was investigated relative to their depth distribution in summer 1995 in the Kongsfjord (79°N; 12°E, Ny Ålesund, Spitsbergen, Norway). Photoinhibition of photosynthesis was induced by exposure of algae from different water depths to a high photon fluence rate of 500 μmol m−2 s−1 for 2 h. Changes in optimal quantum yield (F v/F m) were measured during the inhibition phase. Recovery of photosynthesis was subsequently induced by dim white light (10 μmol m−2 s−1) and observed as changes in the variable fluorescence. With a newly developed mathematical model different parameters of the response kinetics of inhibition and recovery were calculated and related to the depth distribution of each algal species. It is shown that two components with slow and fast reaction kinetics, respectively, are involved in photoinhibition and recovery of photosynthesis. Their possible molecular bases are discussed. The half-life time (τ) of the inhibition and recovery phases, i.e. the time necessary to reach half maximal response, is clearly related to the depth distribution of the investigated species. Algae collected close to the water surface show a fast reaction of both photoinhibition and recovery and, hence, have a low τ. With increasing depth the reactions become slower and τ increases. τ was highest in deep water algae. Further analysis of the reaction kinetics in Laminaria saccharina shows that the relative proportion of the two kinetics involved change with the collection depth. In contrast, a significant difference in the reaction rates of both kinetics was not observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002270050329
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  • 5
    Digitale Medien
    Digitale Medien
    Zeaxanthin content and the degree of photoinhibition are linearly correlated in the brown alga Dictyota dichotoma (1995)
    Springer
    Marine biology 123 (1995), S. 159-165 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photoinhibition of photosynthesis of the brown alga Dictyota dichotoma was studied by measuring changes of photosystem II fluorescence, oxygen production and xanthophyll pool (zeaxanthin, antheraxanthin and violaxanthin). The experiments were carried out with a pulse-amplitude modulation fluorometer (PAM), a homemade oxygen measuring device and high performance liquid chromatography (HPLC) for pigment analysis. Increasing fluences of a photoinhibitory white light caused a decrease of Fv/Fm (ratio of variable to maximal fluorescence), a decrease of oxygen production and concomitantly an increase in the contribution of zeaxanthin to the xanthophyll pool. Fv/Fm and oxygen production rate both showed a negative linear correlation to the zeaxanthin-xanthophyll pool ratio of D. dichotoma. Dithiothreitol (DTT), an inhibitor of the de-epoxidase of the xanthophyll-cycle, suppressed the interconversion from violaxanthin to zeaxanthin and the decrease of the initial fluorescence (F o) during strong-light irradiation. However, DTT was not able to prevent a decrease of Fv/Fm. With DTT, higher fluences of inhibitory white light were necessary to cause the same decrease of Fv/Fm as in the controls without DTT. The results indicate that the xanthophyll-cycle may play an important role in dynamic photoinhibition and recovery of photosynthesis in D. dichotoma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00350335
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  • 6
    Digitale Medien
    Digitale Medien
    UV-radiation can affect depth-zonation of Antarctic macroalgae (1998)
    Springer
    Marine biology 131 (1998), S. 597-605 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Due to depletion of stratospheric ozone over polar regions of the Northern and Southern Hemispheres UV-B-radiation has increased at the surface of the earth. Measurements of variable chlorophyll fluorescence were conducted to document UV-induced photoinhibition of photosystem II in cultivated macroalgae with different depth distributions in Antarctica. The reactions during artificial UV-exposure were observed on a short time scale (hours) and in light–dark cycles over several days. The nine species of investigated macroalgae show great differences in UV-tolerance of the photosynthetic process. Photosynthesis of the studied green algae was inhibited to a minor degree, while the brown algae showed an intermediate inhibition of photosynthesis. The response of the studied red algae varied with species. The differences in the degree of inhibition and recovery of photosynthetic efficiency and capacity indicate that UV-radiation is one important factor affecting the vertical distribution of macroalgae in nature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002270050351
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