CIRAS-3 Operation Manual V. 1.09
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Section 10. Measuring Chlorophyll Fluorescence
with CFM-3
The CFM-3 Chlorophyll Fluorescence Module (Part Number CRS306) is an optional accessory that can
be used with the PLC3 Universal Leaf Cuvette for simultaneous measurement of photosynthesis and
chlorophyll fluorescence. It can also be used for independent measurement of chlorophyll fluorescence if
desired. Prior to measurement of chlorophyll fluorescence, we strongly recommend a review of the
following publication:
Baker NR (2008) Chlorophyll Fluorescence: A Probe of Photosynthesis In Vivo. Annu.
Rev. Plant Biol. 59: 89-113
When performing measurement of chlorophyll fluorescence you MUST make sure that the glass
window (supplied by PP Systems) is fitted to the leaf cuvette head. This window will have the
letter “P” etched in the lower left hand corner.
To verify or change the window on your PLC3 Leaf Cuvette refer
Replacement of PLC3 Glass Window
on page 201 for instructions on how to replace the window.
Overview of Chlorophyll Fluorescence
The Basics
In basic terms, chlorophyll fluorescence is light re-emitted from the chlorophylls, mainly chlorophyll a (chl
a) in Photosystem II (PSII). 95% of chlorophyll fluorescence is from PSII, at room temperature. We
measure chl a because
in vivo
the energy absorbed by chl b is transferred to chl a. It is chl a
fluorescence that changes as a response to changes in physiology. When illuminated, chlorophyll is
excited to a higher energy state. This excitation energy must be dissipated or transferred to avoid photo-
oxidative damage. De-excitation of chlorophyll a leads to one of three processes:
•
Photochemistry (electron transport)
•
Heat dissipation (non-photochemical processes)
•
Fluorescence (emission of red photons, red shift)
Chlorophyll fluorescence represents about 1-3% of the total energy dissipated. Exposing a leaf to actinic
light results in a competition among the three processes. Fluorescence rises at first because induction of
photosynthesis is relatively slow. Then, as photosynthetic rate increases (photochemistry) and heat
dissipation increases (non-photochemical events), the amount and yield of fluorescence decreases.
