opti-sciences OS1p, Руководство пользователя

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The first measurement is taken with no actinic illumination and either dark adaptation or
“quasi-dark adaptation”. While the number of steps, the intensity of each step, the length
of time for actinic illumination at each step, and whether one steps up or down can be
variables in RLCs. Some fluorometers offer only a programmed routine that limit
choices. The second measurement is usually low in the 10 to 50 umol range, and the last
two steps are usually above saturation levels. Ralph (2005) recommends that saturation
should be at or above 1000 umols. Low light leaves require a different intensity range for
measurement than high light leaves. Intensities above 100 umols will commonly saturate
low light leaves.
The length of actinic illumination is also programmable in some fluorometers. Times of 5
seconds, 10 seconds, 30 seconds, 40 seconds, 50 seconds and 60 seconds have been used.
Ralph (2004) indicates that Rapid light curves should provide the shortest actinic light
time possible to prevent plants from reaching steady-state or causing photoacclimation.
The minimum length for actinic time at each step is governed by the time it takes for the
saturation pulse fluorescence signal to relax according to Ralph (2005). High light leaves
tend to relax faster than low light leaves according to Ralph. Ralph finds that 10 seconds
works for the samples he has measured.
Ralph also shows that all RLC cardinal points, including ETR
max ,
change substantially
with different actinic step times.
Since RLC vary significantly at different times of day because of different light history
(Rascher 2000)., it is recommended that the data from several light curves, taken at
different times of day, should be added together and then subjected to light curve fitting
software (Rascher 2000).
Saturation Pulse Duration
The ideal saturation pulse duration is different for higher plants than for algae and
cyanobacteria. The OS1p has a special software routine that provides the optimal
duration value if the saturation flash duration is long enough to fully saturate PSII
reaction centers. In previous generations, it was important to more closely match
saturation duration with the plant type. For example, land plants require a duration of
between 0.5 seconds to 1.5 seconds for correct measurement. Algae and Cyanobacteria
require a duration time of 25 to 50 msec (Schreiber 1995). In the past, times that were too
short would not allow the full saturation of PSII, even at the highest light intensities.
Saturation pulses that were too long, would include a form of saturation pulse NPQ, that
would lower the average saturation pulse intensity value, and produce an error.
(Roseqvist & van Kooten 2006)
The OS1p has a software routine that provides the highest eight-point rolling average
intensity value on the top of the saturation pulse peak. This means that it looks only at the