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turn-overs of Q
A
According to Schreiber (1995). The measuring file only displays ten points
for a one second saturation pulse duration. The machine actually measures 320 points in one
second, and gives the highest eight point rolling average as an Fm’ measurement value. This
automation feature, ensures that the optimal duration is always provided as long as the
duration is set long enough.
Algae and cyanobacteria saturation pulse duration - new feature:
The ideal saturation pulse duration for algae and cyanobacteria range from 0.025 seconds and
0.050 seconds (Schreiber 1995). When using the OS1p for algae work, the OS1p uses a
special algorithm that finds the highest eight point rolling average at the top of the saturation
pulse. The eight point average represents a time of 25ms. Therefore, finding the optimal
saturation duration is always achieved for algae without testing. With a saturation pulse
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.
Length of quenching test.
The leaf must be at steady state photosynthesis before most quenching measurements are
made. This means that the leaf is exposed to a specific light level for between fifteen and
twenty minutes. Due to the fact the fluorometer light intensity changes due to increased heat
while the actinic light source is on, we recommend that quenching tests be taken after twenty
five to thirty minutes of actinic light exposure. The light intensity change is most significant
during the first five minutes as the fluorometer warms up due to the actinic light source.
By extending the test measuring time, the remaining intensity change becomes insignificant
and steady state is reached. The actinic light level can be measured if a PAR Clip is used with
a shroud or it is used in a darkened room.
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