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Cookbook checklist before making Rapid Light Curve measurements.
Fm’ is maximum fluorescence in a light adapted environment. F’ is the fluorescence
signal in a light adapted environment.
Y(II) is = (Fm’ – Fs’) / Fm’ =
)
F/Fm’
relative ETR = Y(II) x PAR x 0.84 x 0.5
1. The first value is zero.
Dark adaption times vary from momentary dark adaption times
of five to ten seconds (Ralph 2005) to longer dark adaptation times (Rascher 2000).
RLCs can provide different cardinal values depending on the time of day, and the dark
adaptation time used. In other words, the results vary with light history.
2. Light history correction.
Some researchers recommend taking RLC at different times
of day, and overlaying the results to reduce the effects of light history (Rascher 2000)
3. RLC can be used on below canopy leaves in the field, algae and cyanobacteria
.
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).
4. Y(II) and relative ETR values vary with light level and with temperature
. The
higher the light level, the lower the Y(II) value. When measuring Y(II) in the field, it is
extremely important to measure leaf irradiation or light level at the leaf and leaf
temperature. Comparing Y(II) values taken at different light levels and different heat
levels introduces a significant error unless it is the change at different light levels and
heat levels that is of interest. This is commonly done with a PAR Clip. If a PAR clip is
used, then a shroud must also be used.
5. Shade leaves vs. Sun leaves
. – The Y(II) and cardinal RLC values will be different
on sun leaves than on shade leaves (Ralph 2005). Most shade leaves will saturate at about
300
:
mols, and most sun leaves will saturate below 1,500
:
mols. (Ralph 2005).
6. When setting the steps in a RLC.
Most should be at an intensity level below
saturation level. At least one intensity value should be above saturation level. (Ralph
2005).
7. Steps can go up or down.
(Rascher 2000).
8. Actinic light step time.
These range from ten seconds, to about two minutes. Ralph
(2005) uses ten seconds, while Rascher (2000) and Herlory (2007) found greater
repeatability with longer actinic step times.
9. Residual saturation pulse NPQ.
It takes one to two minutes for saturation pulse NPQ
to fully dissipate. This means that there is some build up of saturation pulse NPQ with
each actinic step that is shorter than one to two minutes. Saturation pulse NPQ reduces
the Fm’ value.
Содержание OS1p
Страница 108: ...108 Setting saturation pulse width...
Страница 148: ...148 Microsoft Windows Screen on a PC Microsoft Windows Screen on a PC Select Excel...
Страница 173: ...173 Y II data file format...
Страница 174: ...174 Quenching data file format Hendrickson Klughammer equations...
Страница 175: ...175 RCL Rapid Light Curve data format...