CHAPTER 12 MEASUREMENTS WITH THE MINI-PAM
The photodetector is a PIN-photodiode which displays linear
response with light intensity changing by factors of more than 10
9
.
Hence, this measuring system tolerates extreme changes in light
intensity (up to several times the intensity of full sun light) even at
weak measuring light intensities. This property is essential for
correct determinations of photochemical quantum yield via the
fluorescence parameters Fv/Fm or ∆F/Fm' and of minimal and
maximal fluorescence yields, Fo and Fm (see 12.1 and 12.3.4).
Fig. 11: Schematic view of the PAM measuring principle
Due to the PAM measuring principle saturation pulse induced
fluorescence changes can be very selectively and reliably analyzed in
terms of photosynthetic activity. With the MINI-PAM, just like with
all PAM fluorometers, even small values of ∆F induced by a
saturation pulse can be relied on. This can be simply tested by
applying a saturation pulse (via START) to a fluorescing sample, like
the FLUORESCENCE STANDARD (Blue plastic filter) delivered
with the MINI-PAM, which is not capable of photochemical energy
conversion. With such a sample invariably YIELD = 0.000 is
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