HANSATECH FMS1, Manual

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64 FMS 1 - Fluorescence Monitoring System
© 2017 Hansatech Instruments Ltd
-2 s -1 (effectively
checks presence of the PAR sensor)
If the measured values used during the calculation of a derived parameter do not obey the above
rules any suspect calculated parameter will be flagged in the format “?? calculated number”. The
cause of such flags is usually easy to trace by manually calculating the parameter from the “raw”
data that is always presented in the “Parameters Window”.
The phi PSIIR function
Adaptation to high irradiance can involve significant changes in the conformation of the
photosynthetic apparatus which result in non-photochemical energy dissipation in the PSII
antennae, before energy reaches the reaction centres (Horton et al. 1991 Horton and Ruban 1994).
Failure to account for this effect can lead to inaccuracies in calculation of the relative
contributions of photochemical and non-photochemical energy dissipation. This problem can be
overcome by transiently shading the sample and using a far-red light source to preferentially
excite PSI relative to PSII; electrons
are drawn through the electron transport chain effectively “opening” PSII reaction centres and
allowing measurement of a light-adapted Fo, usually given the notation Fo’. The
f
PSIIR function
initiates the following sequence of events to make these measurements:
1. Values of PAR and temperature are logged from the leaf-clip (these will be zero if the clip is not
connected),
2. The steady state fluorescence value (Fs) is determined by averaging the fluorescence signal
under the ambient light,
3. A saturation pulse, defined by the intensity and duration values in the “Pulse” edit boxes, is
applied and Fm’ stored as the average of the highest consecutive values,
4. 3 sec after the pulse the sample should be temporarily dark-adapted by shading the sample (the
FMS actinic source is automatically switched off), and a 5 sec far-red pulse is applied ,
5. The fluorescence decline is tracked during the far-red pulse with the minimum yield stored as
Fo’,
6. At the end of the function the FMS actinic source is switched back on.
The
f
PSIIR function calculates and writes the following parameters (using the measurement of Fo’)
to the “Parameters Window”. The error trapping rules described in The phi-PSII function . are used
Parameter Measurement Units Derivation
PAR Incident
photosynthetically
active radiation
µmolm
-2
s
-1
Temp Incident °C