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21Author    MarcelA K Jansen, Klaus PfisterRequires cookie*
 Title    Conserved Kinetics at the Reducing Side of Reaction-Center II in Photosynthetic Organisms; Changed Kinetics in Triazine-Resistant Weeds  
 Abstract    The decay o f chlorophyll variable fluorescence after a "single turnover" flash is generally assumed to represent the reoxidation o f the reduced quinone Qa. We have observed that the kinetics o f this decay are very similar in a wide variety o f species. Comparing 28 different spe­ cies, we found an average half decay time o f 314 ± 4 6 (isec. N o systematic correlations were found between the decay rate and biochemical or physiological specializations such as C 2, C 4 or C A M . This indicates that structural as well as functional factors controlling photosystem II electron transfer between Qa and Qb are highly conserved. Apparently, the freedom for natural structural variations in this region is very limited. Triazine resistant plants, characterized by an altered amino acid sequence o f the D 1 protein, have clearly decreased rates o f Qa/Q b electron transfer. We found an average half decay time o f 946 ± 100 jisec (5 species). However, this three-fold decrease is much less than previously re­ ported. Therefore, if alterations o f photosystem II electron transfer efficiency contributes to an often reported reduction o f "ecological fitness", this contribution is smaller than was hitherto assumed. 
  Reference    Z. Naturforsch. 45c, 441—4 (1990); received November 27 1989 
  Published    1990 
  Keywords    Chlorophyll Fluorescence, Evolution, Photosystem II, Triazine Resistance, p sb A Conservation 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0441.pdf 
 Identifier    ZNC-1990-45c-0441 
 Volume    45 
22Author    U. Lrich Schreiber, H. Einz, Reising, C. Hristian, N. EubauerRequires cookie*
 Title    Contrasting pH-Optima of Light-Driven 0 2-and H 20 2-Reduction in Spinach Chloroplasts as Measured via Chlorophyll Fluorescence Quenching  
 Abstract    Quenching analysis o f chlorophyll fluorescence by the saturation pulse method is used to investigate the pH-dependency o f 0 2-dependent electron flow in intact spinach chloroplasts with high ascorbate peroxidase activity. When carboxylase/oxygenase activity is blocked, p h o­ tochem ical and non-photochemical quenching are initially low and increase with illumination time. Quenching shows a pH-optimum around pH 6.5, but only when ApH-formation is al­ lowed. It is suggested that overall 0 2-dependent electron flow involves two major com ponents, namely 0 2-reduction (M ehler reaction) and reduction o f the H 20 2 formed in the Mehler reac­ tion, involving enzymic activity o f ascorbate peroxidase and m onodehydroascorbate reduc­ tase. The separated pH-dependencies o f light driven 0 2-reduction (presence o f K C N) and o f H 20 2-reduction (anaerobic conditions) reveal contrasting pH-optim a around pH 5 and 8.5, re­ spectively. Energy-dependent, dark relaxable non-photochem ical quenching is not observed with 0 2-reduction but with H20 2-reduction, and only at pH-values above 6.5. The relevance o f these findings with respect to regulation o f photosynthetic electron flow is discussed. It is sug­ gested that upon limitation o f assimilatory electron flow 0 2-dependent non-assim ilatory flow is responsible for ApH-formation, by which it is autocatalytically stimulated. It is proposed that this autocatalytical reaction sequence is the basis o f the so-called "Kautsky effect" o f chlorophyll fluorescence induction. 
  Reference    Z. Naturforsch. 46c, 635 (1991); received March 6 1991 
  Published    1991 
  Keywords    Chlorophyll Fluorescence, Mehler Reaction, Ascorbate Peroxidase, Energy Dependent Quenching, Photosynthesis Regulation 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0635.pdf 
 Identifier    ZNC-1991-46c-0635 
 Volume    46 
23Author    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 
24Author    Juliane Peters, M. Soledad, Jim Énez, Domingo MoralesRequires cookie*
 Title    Effect of Extreme Temperature on Quantum Yield of Fluorescence and Membrane Leakage of the Canarian Endemic Pine (Pinus canariensis)  
 Abstract    The effect of extreme temperature on the quantum yield of fluorescence and membrane leakage of Pinus canariensis growing in 5 stands at different altitudes and orientation in Tenerife (Canary Islands, Spain) was determined. Needles were collected from the field and transferred to the laboratory where they were kept in a closed chamber with water-saturated air overnight. Then they were exposed for 30 minutes in plastic bags in a water bath at temperature treatments with steps of 2K between 56 °C and -2 4 °C and the effect was deter­ mined immediately and 24 hours after the treatment by chlorophyll fluorescence and electro­ lyte leakage. Needles presented incipient damage at temperatures ranging from -5 to -1 0 °C depending on the altitude and orientation of the stand. The results were more evident when the mea­ surements were done 24 hours after the cold treatment and values were consistent with the electrolyte leakage results. Different resistance to high temperature depending on the alti­ tude and orientation was also found, varying the temperature for incipient damage from 42 to 44 °C detected with the fluorescence parameters but not with the leakage of electrolytes which was not found until 50 °C. The amplitude of thermal limits for photosynthetic effi­ ciency alteration in needles of P. canariensis was relatively narrow and similar to that of evergreen Canarian laurel forest trees. 
  Reference    Z. Naturforsch. 54c, 681—6 (1999); received December 10 1998/February 20 1999 
  Published    1999 
  Keywords    Pinus canariensis, Low Temperature, High Temperature, Altitudinal Gradient, Chlorophyll Fluorescence, Electrolyte Leakage 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0681.pdf 
 Identifier    ZNC-1999-54c-0681 
 Volume    54 
25Author    Domingo Morales3, Juliane Peters3, M. Soledad, Jim Énez3, Michael Tauszb, Astrid Wonischb, Dieter GrillbRequires cookie*
 Title    Gas Exchange of Irrigated and Non-Irrigated Pinus canariensis Seedlings Growing Outdoors in La Laguna, Canary Islands, Spain  
 Abstract    Chlorophyll fluorescence, gas exchange, water potential and relative water content were measured in the needles of five year old seedlings of Pinus canariensis in order to know their response to mild water stress. Two trial plots of ten plants per plot, of similar age and characteristics were irrigated daily until the experiment was undertaken, then one of the plots was left without watering while the other one was irrigated as before. After a week of treatment, the water potential at midday did not change in any of the irrigated or non-irrigated plants maintaining around -0 .4 MPa, and the relative water content changed from 93% in irrigated to 84% in non-irrigated seedlings. The stomatal conductance decreased 60% in non irrigated plants and as a result C 0 2 assimilation decreased by 50% and transpiration was reduced at a higher proportion (70%), indicating a good control against water loss, before any change in water status in the needles could be observed suggesting an isohydric water economy in this plant. 
  Reference    Z. Naturforsch. 54c, 693—6 (1999); received December 14 1998/March 21 1999 
  Published    1999 
  Keywords    Pinus canariensis, Mild Water Stress, Gas Exchange, Water Potential, Chlorophyll Fluorescence, Seedlings 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0693.pdf 
 Identifier    ZNC-1999-54c-0693 
 Volume    54 
26Author    Claus Buschm, HartmutK. LichtenthalerRequires cookie*
 Title    Contribution of Chlorophyll Fluorescence to the Reflectance of Leaves in Stressed Plants as Determined with the VIRAF-Spectrometer  
 Abstract    Reflectance spectra allow the early detection of stressors causing differences in pigment content as well as changes of leaf tissue structure and photosynthetic activity. The reflectance decreased with increasing Chi content in greening bean leaves. In stressed leaves, in turn, the reflectance increased with decreasing Chi content. This also caused a shift of the red reflection rise ("red edge") to shorter wavelengths ("blue shift") associated with a blue shift of the inflection point of the red edge. The contribution of the red and far-red Chi fluores­ cence to the reflectance signal at the red edge of the spectrum and the shift of the wavelength position of the inflection point are demonstrated and discussed. 
  Reference    Z. Naturforsch. 54c, 849 (1999); received May 20 1999 
  Published    1999 
  Keywords    Chlorophyll Fluorescence, Red Edge of Reflectance, Remote Sensing, Spectroscopic Techniques, Stress Detection 
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 TEI-XML for    default:Reihe_C/54/ZNC-1999-54c-0849.pdf 
 Identifier    ZNC-1999-54c-0849 
 Volume    54