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'Chlorophyll Fluorescence' in keywords Facet   Publication Year 1994  [X]
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1Author    StefanD. Renkard3, JürgenM. Aguhnb, D. Ietm Ar Knoppik3Requires cookie*
 Title    Simultaneous Gas-Exchange and Fluorescence Measurements with Ozone-Fumigated Spruce  
 Abstract    A method was developed for carrying out gas-exchange and chlorophyll-fluorescence measurements simultaneously during fumigation of spruce twigs with peroxidic photooxi­ dants. It is thus now possible to investigate how a pollutant affects distinct sectors of the photosynthetic apparatus of the plant: whereas fluorescence reveals any changes in the pri­ mary light reaction, C 0 2 gas-exchange measurements supply information about the bio­ chemical reactions of the Calvin cycle. Results of short-time fumigation with 750 ppb ozone are presented here. Gas-exchange and fluorescence data are affected strongly in early sum­ mer, but not in autumn. The assimilation rate decreases significantly: primarily as a result of Rubisco activity and possibly because of direct inhibition of the electron-transport chain as well. Closure of the stomata leads to further reduction in the assimilation rate. Though no damage becomes visible on the needles, the perturbance of the photosynthetic apparatus caused by ozone fumigation is not reversible within 24 h. 
  Reference    Z. Naturforsch. 49c, 819—833 (1994); received June 21 1994 
  Published    1994 
  Keywords    Spruce, Photosynthetic Apparatus, Gas Exchange, Chlorophyll Fluorescence, Ozone Fumigation 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0819.pdf 
 Identifier    ZNC-1994-49c-0819 
 Volume    49 
2Author    Ulrich SchreiberRequires cookie*
 Title    New Emitter-Detector-Cuvette Assembly for Measuring Modulated Chlorophyll Fluorescence of Highly Diluted Suspensions in Conjunction with the Standard PAM Fluorometer  
 Abstract    A new emitter-detector-cuvette assembly for the standard PAM fluorometer is described which leads to substantial improvement of signal/noise ratio and increased flexibility with respect to the choice of excitation and emission wavelengths. These features are particularly useful for work with very dilute suspensions of unicellular algae and isolated chloroplasts. Instead of fiber optics perspex rods are applied for guiding excitation light to a mirrored 10x10x45 mm cuvette and from there at 90° angle to the photodetector, similarly as recently reported for a PAM fluorometer based on Xe-flash measuring light (Schreiber et al. (1993), Photosynth. Res. 36, 65-72). While the detection limit of the new system does not reach that of the Xe-PAM fluorometer, it is approximately two orders of magnitude higher than that of the standard system. Rapid induction kinetics can be measured at low chlorophyll concen­ trations down to 0.1 (.ig-ml '. Satisfactory quenching analysis for detection of active chloro­ phyll concentration is still possible at 5 |ig chlorophyllT '. The various optical factors con­ tributing to the improved sensitivity are analyzed. An accessory device is described by which the frequency of the measuring light pulses generated by the PAM fluorometer is lowered in order to reduce the actinic effect of the measuring light. The performance of the new system using different excitation and emission wavelengths is demonstrated in measurements with green algae, cyanobacteria and leaves. Applying a newly available blue light-emitting diode with 450 nm peak emission, short wavelength fluorescence enriched in PS II emission can be measured, which is characterized by high values of variable fluorescence relative to maximal fluorescence. Using measuring light covering five different wavelength ranges the fluorescence contributions from cyanobacteria and green algae can be distinguished on the basis of distinct differences in their excitation spectra. This approach should become useful for an estimation of content and activity of different types of phytoplankton in natural surface waters. 
  Reference    Z. Naturforsch. 49c, 646—656 (1994); received May 18/July 7 1994 
  Published    1994 
  Keywords    Chlorophyll Fluorescence, Photosynthesis, PAM Fluorometer, Quenching Analysis, Unicellular Algae, Cyanobacteria, Phytoplankton 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0646.pdf 
 Identifier    ZNC-1994-49c-0646 
 Volume    49