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  • 1
    Electronic Resource
    Electronic Resource
    Optimized nitrate reductase assay predicts the rate of nitrate utilization in the halotolerant microalga Dunaliella viridis (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 99-106 
    Details
    ISSN: 1573-5176
    Keywords: Nitrate reductase ; in situ enzymatic activity ; Dunaliella viridis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An in situ method for measuring nitrate reductase (NR) activity in Dunaliella viridis was optimized in terms of incubation time, concentration of KNO3, permeabilisers (1-propanol and toluene), pH, salinity, and reducing power (glucose and NADH). NR activity was measured by following nitrite production and was best assayed with 50 mM KNO3, 1.2 mM NADH, 5% 1-propanol (v/v), at pH 8.5. The estimated half-saturation constant (Ks) for KNO3 was 5 mM. Glucose had no effect as external reducing power source, and NADH concentrations 〉1.2 mM inhibited NR activity. Nitrite production was linear up to 20 min; longer incubation did not lead to higher nitrate reduction. The use of the optimized assay predicted the rate of NO 3 − removal from the external medium by D. viridis with high degree of precision.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007978512458
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of different levels of CO2 on photosynthesis and cell components of the red alga Porphyra leucosticta (1999)
    Springer
    Journal of applied phycology 11 (1999), S. 455-461 
    Details
    ISSN: 1573-5176
    Keywords: CO2 ; inorganic carbon ; macroalgae ; photosynthesis ; PAM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis and cell composition of Porphyraleucosticta discs grown at low (〈 0.0001% in air), current (control) and high (1% CO2 in air)inorganic carbon (Ci) concentrations were analyzed. Carbohydrate content in discs grown at high Ci increased (15.1 mg g-1 FW) with respect to the control (6.4 mg g FW-1), whereas soluble protein content decreased to one-third (5.6 to2.1 mg g-1 FW). Carbohydrate content was unaffected and soluble protein slightly increased in discs grown at low Ci. As a consequence of these changes, a lower C/N molar ratio (8.6) was found in the discs grown at low compared to high Ci(12.4). Nitrate reductase activity increased at high Ci from 0.3 ± 0.2 to 1.7 ± 0.4 μmolNO2 - g-1 FW h-1indicating that reduction and assimilation of nitrate were uncoupled. The response of photosynthesis to increasing irradiance, estimated from O2evolution vs. irradiance curves, was affected by the treatments. Maximum quantum yield (Φ O2°) and effective quantum yield (Φ O2) at 150 μmol photon m-2s-1 decreased by 20% and 50%, respectively, at low Ci. These differences could be due to changes in photosynthetic electron flow between PSII and PSI. Treatments also produced changes in maximal (Fv/Fm) and effective (ΔF/Fm′)quantum yield for photosystem II charge separation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008194223558
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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