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  • 1
    Digitale Medien
    Digitale Medien
    Stable vinyl cations 4: Carbon-13 nmr spectroscopic observation of an α-ferrocenyl-vinyl cation
    Amsterdam : Elsevier
    Tetrahedron Letters 26 (1985), S. 1493-1496 
    Details
    ISSN: 0040-4039
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://linkinghub.elsevier.com/retrieve/pii/S0040-4039(00)98533-2
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Hydrodynamics, diffusion-boundary layers and photosynthesis of the seagrasses Thalassia testudinum and Cymodocea nodosa (1994)
    Springer
    Marine biology 118 (1994), S. 767-776 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic rates of aquatic plants frequently increase with increasing current velocities. This is presumably due to a reduction in the thickness of the diffusion boundary-layer which allows for a higher carbon availability on the plant surface. Blades of the seagrasses Thalassia testudinum and Cymodocea nodosa exposed to different current velocities under controlled laboratory conditions, showed increased photosynthetic rates with increasing flow only at low current velocities (expressed as blade friction velocities, u *). Carbon saturation of photosynthetic processes occurred at a relatively low u * level (0.25 cm s-1) for T. testudinum collected from a calm environment compared to C. nodosa (0.64 cm s-1) collected from a surf zone. No further enhancement of photosynthetic rates was observed at higher u * levels, suggesting limitations in carbon diffusion through the boundary layer below critical u * levels and possible limitations in carbon fixation by the enzymatic system at higher u * levels. These results, as well as those of previous theoretical studies, assumed the flow on the immediate seagrass-blade surface to be hydrodynamically smooth. The presence of epiphytes and attached debris causes the surface of in situ seagrass blades to be exposed to flows ranging from smooth to rough-turbulent. As a consequence, the boundary-layer thickness on moderately epiphytized blades under medium to high flow-conditions is not continuous, but fluctuates in time and space, enhancing carbon transport. In situ u * levels measured directly on blades of seagrasses indicate that T. testudinum and C. nodosa can be exposed to conditions under which the boundary layer limits photosynthesis during short periods of time (milliseconds) during low-energy events. As waves cause the thickness of the diffusion boundary-layer to fluctuate constantly, carbon-limiting conditions do not persist for prolonged periods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00347527
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  • 3
    Digitale Medien
    Digitale Medien
    In vitro studies of the submerged angiospermRuppia maritima: Auxin and cytokinin effects on plant growth and development (1991)
    Springer
    Marine biology 110 (1991), S. 1-6 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Axenic tissue cultures ofRuppia maritima L. were established and propagated clonally in vitro from terminal rhizome segments collected from Tampa Bay, Florida, USA. Cultures were maintained in a base medium consisting of synthetic seawater supplemented with half-strength Murashige and Skoog salts and 1% sucrose at pH 5.6. The effects of five cytokins [6-furfurylaminopurine (kinetin), 6-benzylaminopurine (BAP), 2-isopentyladenine (2iP), 6-(4-hydroxy-3-methyl-but-2-enylamino) purine (zeatin), andn-phenyl-n′-1,2,3-thidiazol-5′yl urea (thidiazuron)] and one auxin [napthalene acetic acid (NAA)] on explant growth and development were investigated. Cytokinin additions resulted in a 3- to 4-fold increase in nodal production, branching, and biomass ofR. maritima after 12 wk in culture. Cultures responded in a dose-dependent manner to 2iP but exhibited broad dose-response curves to kinetin, BAP, zeatin, and thidiazuron. NAA addition resulted in increased leaf and internodal lengths, but reduced the number of leaves per node and the rhizome biomass. The addition of NAA almost completely suppressed root growth in media without cytokinins and had an antagonistic effect on nodal production and branching in cytokinin-supplemented media.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01313085
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  • 4
    Digitale Medien
    Digitale Medien
    The effect of water flow on photosynthetic processes of the alga Ulva lactuca L. (1993)
    Springer
    Hydrobiologia 260-261 (1993), S. 457-462 
    Details
    ISSN: 1573-5117
    Schlagwort(e): friction velocity ; boundary layer ; carbon ; Ulva
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic rates of aquatic macrophytes are affected by the diffusion of carbon through the boundary layer which decreases with increasing flow velocities. This is shown by a significant increase in photosynthetic rates of Ulva lactuca fronds exposed to friction velocities (u *) between 0.0 and 0.3 cm s−1. No further increase in photosynthetic rates is observed at u * values between 0.3 and 1.0 cm s−1. Stagnating flow conditions at saturating light levels caused a 29% reduction in photosynthetic rates. Experiments in a closed system indicate that Ulva may utilize internal carbon sources during periods of stagnation. On a subtidal rock directly exposed to wave action, Ulva lactuca is not exposed to such conditions while in a wave flushed intertidal pool stagnation occurs during very short time intervals based on in situ measurements of u * levels on fronds of this species using a microprocessor-controlled, autonomous recorder and hot-film sensors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00049056
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