CHAPTER 5 IMPORTANT POINTS
(...E). The plot of ETR vs. PAR corresponds to a light-response
curve of photosynthesis (see 12.3.9).
4) When YIELD is measured under field conditions, it is essential
that the leaf position and effective PAR are not inadvertently
changed. During the actual measurement, the fiberoptics must be
stably fixed with respect to the leaf surface for ca. 2 s, e.g. with
the help of the Leaf-Clip Holder 2030-B.
5) Dark YIELD-measurements require special conditions (see also
12.3.1). As already pointed out in 3), such measurements cannot
give information on the overall
photosynthetic performance. They
are useful to specifically assess the state of PS II, for example
following light stress treatment. In this case, it is essential, that
the measuring light does not induce any significant increase of
fluorescence yield. For this purpose, the MODE-menu point 5
provides the possibility of applying the measuring light in short
pulse bursts, thus cutting its integrated intensity to 1/5 (see
12.3.2).
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