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Measurement of non-photochemical quenching using the JTS-150 pump probe spectrometer – Application Note 5.

Latest updated: September 2, 2021


In this application note, we describe how to measure Non- Photochemical Quenching (NPQ) using the JTS-150. This method has been long utilized by the previous models of JTS and provides data that is analogous to a pulsed-amplitude modulated (PAM) fluorometer. PAM fluorometers have been powerful tools that were based on the model that absorbed solar radiation which has 3 possible fates: to be released as heat, fluorescence, or drive photochemistry. The photochemical pathway leads to a quenching of observed fluorescence that is therefore referred to as photochemical quenching.


Chlorophyll fluorescence is a widely used technique and has been the subject of several excellent reviews that we would recommend before starting experiments if the techniques are unfamiliar, please see [1, 2, 3]. Separation of fluorescence quenching into photochemical and non-photochemical components was first achieved by the addition of 3-(3,4- dichlorophenyl)-1,1-dimethylurea (DCMU) to intact chloroplasts and Chlorella cells at points throughout the fluorescence induction curve. DCMU inhibits electron transfer from QA to the secondary quinone acceptor of PSII (QB), which results in a rapid reduction of QA and an in-crease in fluorescence as photochemical quenching is prevented. The development of PAM flu- orometers that use weak modulated measuring beams in which phase and frequency decoding are used to detect fluorescence yield changes enabled the routine, nondestructive, quantitative determination of photochemical and non-photochemical processes in leaves.

Photosynthesis Non Photochemical quenching (NPQ) Chlorophyll fluorescence PAM fluorescence Pump probe spectrometer JTS-150

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