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.