opti-sciences OS1p - What Are the Limitations of RLC

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highest average eight points over a 25msec time frame. It also means that one setting can
work well for higher plants, algae, or cyanobacteria.
What are the limitations of RLC?
The rapid light curve is affected by immediate light history and longer term light history
(Rascher 2000, (Ralph 2005). It is also affected by time required to dark adapt (Rascher
2000), NPQ related to the previous light step (Herlory 2007), and in many cases the NPQ
from the previous saturation pulse (Roseqvist and van Kooten 2005). These factors will
be discussed below.
Rascher (2000) explored the value and limitations of Rapid Light Curves in detail and
found that not only did the results from RLC and ETRmax change dramatically depending
on the time of day that they were measured, but that they also provided different " and Ik
information with different dark adaptation times. The slopes were found to be steeper
with 30-second dark adaption than with 30-minute dark adaption. ETRmax was found to
be the same with both dark adaption times. Since light history changes the results of
RLCs, Rascher recommends making measurements at different times of day, combining
the data, and then feeding it into light curve fitting software.
Ralph (2005) recommends a 5-10 second dark adaption time to measure the effects with
no actinic light to drive photosynthesis. This allows for rapid reoxidation of QA without
significant relaxation of non-photochemical quenching. Ralph also recommends the 5-10
second dark adaptation to prevent the deactivation of rubisco and to prevent a rubisco
reactivation induction effect.
Related information in this area includes the following: Full rubisco deactivation takes
between 9 to 18 minutes in Algae and up to 28 minutes in land plants (MacIntyre 1997).
Full reactivation of Rubisco takes between 3 to 4 minutes for both algae and land plants
(MacIntyre 1997). Consalvey (2004) found that far red light illumination used to activate
PSI was very helpful in the complete reoxidizing QA in a short period of time, whereas
dark adaptation took much longer on his samples.
Herlory (2007) found that the time of actinic illumination impacts results. Each
successive RLC step adds non-photochemical quenching to the next step. He also found
that the time used for actinic illumination at each step affects the repeatability of the
results. The most repeatable results were achieved with actinic step times of 50 seconds
or longer, and the lowest precision was found with 10 second times.
Roseqvist and van Kooten (2005) found that saturation pulses create a short lived NPQ
that takes between 60 seconds and 120 seconds to fully dissipate, so if the actinic steps
are shorter than that time frame, then each saturation pulse in the RLC will reduce the
yield and ETR values as well.