21
Quenching Measurements, an Overview
(Images from the OS5p)
Puddle Model Kramer Lake Mode Hendrickson Klughammer Lake Model
Dark–Light Pulse modulated Chlorophyll Fluorescence Trace – Screens are taken from the OS5p.
Parameter read outs from the OS1p will be in a separate window but on the same screen, and only one of
the protocols shown, come as standard with the system. Others may be purchased for an additional price.
Introduction:
This article is an overview of the value and limitations of kinetic traces and provides a basic
understanding of photochemical and non-photochemical quenching measurements. The
puddle model, the Kramer lake model, and the Hendrickson /Klughammer & Schreiber lake
model parameters will be reviewed and practical considerations are added to the discussion.
Kinetic traces are used in measuring photoprotective mechanisms, state transitions,
photoinhibition, passive energy dissipation and creating light curves. These measurements are
usually determined when a plant reaches steady state photosynthesis, however, Klughammer
states that Y(NO) is not limited to steady state measurement if his simplified equations are
used. Without a good understanding of the mechanisms that affect the light trace, machine
artifacts and user errors can be included in measurements.
The Fluorescence signal
Fluorescence has been found to provide significant information regarding photosynthetic
processes, plant health, and plant stress measurement. Fluorescence from light that is
absorbed by PSII has been shown to vary with these conditions and allow measurement,
where as PSI fluorescence is low, and does not vary in intensity. The fluorescence signal that
comes from PSII is the result of a competitive process with photochemistry and heat
dissipation (heat dissipation can further be divided into non-radiation decay and
photoprotective regulated heat dissipation). For example, when most of the light is used by
photochemistry, less is given off as fluorescence and heat. PSII has also been found to be
sensitive to most types of plant stress (Baker 2008).
