CIRAS-3 Operation Manual V. 1.09
133
Calc Fluorescence
will be grayed out, indicating that fluorescence data must
be written to the data file. If you previously selected CFM-3, Chlorophyll
Fluorescence Module, the
Calc Fluorescence
box will be checked (enabled)
and
Photosynthesis
will be unchecked (disabled). Both will be grayed out,
indicating that only fluorescence data will be written to the data file.
Initial Fluorescence
phiPSII-SP (
ϕPSII-Single-Pulse)
. If selected, there is no need to dark adapt
the leaf and measurements can begin right away and a single, saturating pulse
applied to the light-adapted leaf sample. The single pulse duration and
intensity can be set in the lower part of the screen under “Saturating Light”.
phiPSII-MP (
ϕPSII-Multi-Pulse)
. If selected, there is no need to dark adapt
the leaf and a “Multi-Pulse sequence can begin right away with multiple,
saturating pulses applied to the light-adapted leaf sample. The Multi-Pulse
duration and intensity settings (up to 5 steps) can be set in the lower part of the
screen under “Saturating Light”.
Fv/Fm.
If selected, you will need to allow the plant to dark acclimate prior to
measurement. If performing Fv/Fm measurements we recommend doing so at
night or before sunrise. This will ensure that the leaves are completely dark
adapted and will allow for more measurements to be taken over shorter
periods. As an added precaution you can cover the CFM-3 with a dark cloth to
ensure that the inside chamber is completely dark. Set the
Initial Dark Adapt
Period
of your choosing. Longer dark adapt period are required for plants that
have been exposed to high light and shorter periods for plants that have been
in the dark or low light.
To determine the effective dark adaptation period you will need to identify the
point at which F
v
/F
m
does not increase with an associated increase of the dark
adaptation period. In the example below, the leaf sample is sufficiently dark-
adapted after 20 minutes, since longer dark adaptation periods did not result in
higher F
v
/F
m
values. Note that prior light exposure (intensity, duration)
significantly affects the minimum effective dark adaptation period required to
fully re-oxidize (open) PSII photochemistry in the leaf sample.
