Photosynthesis Research

, Volume 36, Issue 1, pp 65–72 | Cite as

PAM fluorometer based on medium-frequency pulsed Xe-flash measuring light: A highly sensitive new tool in basic and applied photosynthesis research

  • Ulrich Schreiber
  • Christian Neubauer
  • Schliwa Ulrich 
Technical Communication


A newly developed modulation fluorometer is described which employs repetitive 1 μs Xe-flashes for excitation light. Similar to the standard PAM Chlorophyll Fluorometer, which uses 1 μs LED pulses for measuring light, the integrated measuring light intensity is sufficiently low to monitor the dark-fluorescence level, Fo. The maximal fluorescence yield, Fm, can be determined with high selectivity upon application of a saturating light pulse. The Xe-PAM displays exceptionally high sensitivity, enabling quenching analysis at chlorophyll concentrations as low as 1 μg/l, thus allowing to assess photosynthesis of phytoplankton in natural waters like lakes, rivers and oceans. Due to high flexibility in the choice of excitation and emission wavelengths, this system also provides the experimental basis for a thorough study of fluorescence and photosynthesis properties of various algae classes with differing antenna organisation. By appropriate modifications, the instrument may as well be used to measure with great sensitivity and selectivity other types of fluorescence (e.g. NADPH-fluorescence), as well as light-scattering and absorbance changes.

Key words

chlorophyll fluorescence PAM fluorometer photosynthesis quenching analysis alga photosynthesis phytoplankton 


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Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • Ulrich Schreiber
    • 1
  • Christian Neubauer
    • 1
  • Schliwa Ulrich 
    • 1
  1. 1.Lehrstuhl Botanik IJullus-von-Sachs-Institut für Biowissenschaften der Universität WürzburgWürzburgGermany

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