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duration of 0.1 seconds, an algorithm that averages only the highest eight points over a 0.025
second time period, saturation pulse NPQ will not reduce the optimal measurement, even if
the duration is set for longer periods of time.
The stepped intensity linear regression mode allows one to determine values with an infinitely
bright light for high light sample conditions. See multi-flash for more details.
The LED actinic light source
An actinic source is a light source that drives photosynthesis. It may be the sun or an artificial
light source. Using an artificial light source has the advantage that it can eliminate the
variability of sun light shading, and partly cloud day cover. The OS1p has a high intensity
white light LED that is used as an actinic light source. This same light source is used for
saturation flashes.
The far-red light source
The peak wavelength for the Far Red source is ~735nm. Far-red light is a light source that
drives PSI without driving PSII. This has the effect of draining the remaining electrons from
PSII quickly to provide a completely oxidized state in PSII. It is used for determination of
Fod or Fo’. Light at these wavelengths allows electron transfer from PSII to PSI, and it allows
the fast re-oxidation of PSII. The far red source may be used in the Fv/Fm protocol to rapidly
re-oxidize PSII before measurement.
During the yield test when artificial internal illumination is used, far red light is filtered out of
both internal illuminators. Therefore, to closely replicate solar radiation that has both PAR
radiation and far-red radiation to drive both PSII and PSI, the far red light should be on during
internal illuminator actinic illumination. Both intensity and duration are adjustable.
The Fiber Optic Light Guide
The optical signals are transferred to and from the sample by a custom-designed trifurcated
fiber optic light guide, with randomly mixed fibers. One end of this fiber bundle has three
BNC (twist-lock) connectors for the three BNC male connectors on the OS1p right side panel.
Any fiber optic BNC connector can be attached to any OS1p BNC connector. In addition
there is a trigger switch on the far end of the bundle from the BNC Connectors. This switch
can be used to take a measurement, or one can press the enter button on the OS1p front panel,
The trigger switch is connected electronically by a wire running down the fiber optic cable,
and attaches to the “remote” port on the right side panel. The other end provides a
comfortable fiber bundle grip and an interface section designed to fit into the many cuvette
options.
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