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Rapid Light Curves (RCL)
Rapid light curves have been heavily used by researchers to study aquatic plants, and for
under canopy research on land. Some traditional fluorescence parameters and methods
run into difficulty when the light level changes rapidly, or when one is studying the
effects of sun flecks. While the measurement of photosynthetic yield only takes a couple
of seconds, it is defined as a measurement taken during steady state photosynthesis, a
process that takes between fifteen and twenty minutes at given light level (Maxwell and
Johnson 2000). Under canopy leaves are exposed to sun flecks and variable illumination.
Traditional photosynthetic yield, ETR, and standard light response curves run into
problems. Wave action, changes in water column depth, tides, currents, clouds and
turbidity constantly change the amount of light that is received by aquatic plants. Of
course, Fv/Fm may be used to measure the health of PSII with some of these situations;
however, the need to study and measure the reaction of plants under changing ambient
conditions and the need to study light saturation characteristics has driven research into
methods such as rapid light curves.
Rapid light curves provide relevant information on the saturation characteristics of
electron transport. (Schreiber 2004). When working with Aquatic plants, and water
column productivity, saturation characteristics are among the most important
determinates. Marra (1978), (Banse and Yong 1990).
Light saturation rate as measured by rapid light curves highly correlates with the
concentration and maximum activity of Rubisco (Macintyre 1997), (Macintyre 1996).
Measured Steady state photosynthetic rates overestimate actual photosynthetic rates in a
variable light environment (Macintyre 1997).
There are many claims about the value of rapid light curves (or RLCs), and some are
controversial. It has been mentioned by Ralph (2005) that a possible reason for rapid
light curves not being more highly used is that researchers are not sure what the data
means, and how reliable the data is. We will provide an overview of the Rapid light curve
and the research regarding RLC.
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