CHAPTER 12 MEASUREMENTS WITH THE MINI-PAM
This and additional information is stored in the MEMORY (see
section 6) and can be transferred via the RS 232 interface to a PC
using the WinControl software (see separate manual) or the
PAMTRANS software (see 9).
Formally, there is no difference between YIELD-measurements
with dark-adapted or illuminated samples. In the former case, F and
M correspond to Fo and Fm (see 12.3.4) and Y corresponds to
Fv/Fm, the maximal photochemical quantum yield (see 12.3.1). In
practice, YIELD-determinations of illuminated samples are more
easy, as the effect of measuring light intensity can be neglected. On
the other hand, the interpretation of YIELD-data from illuminated
samples requires somewhat more background knowledge. Whereas
the dark-adapted state is well defined, there is an infinite number of
light states, mainly determined by quantum flux density (PAR),
illumination time, temperature and the physiological state of the
sample. Therefore, YIELD-measurements should be carried out at
defined light intensities and after defined periods of exposure to
these intensities.
In one of its most common applications, the MINI-PAM assesses
YIELD of plants in their natural light environment under steady-state
conditions. In this case, use of the Leaf-Clip Holder 2030-B with
automatic measurement of PAR and leaf temperature is very
convenient (see 8.3). For adjustment of defined PAR-values the
External Halogen Lamp 2050-HB (see 8.5) can be recommended.
12.3.8 ACT-LIGHT and ACT+YIELD (menu points 12 and 13)
For shorter periods of actinic illumination also the internal
halogen lamp can be used (see 8.1.3). As this leads to internal
heating, illumination times are limited to 5 min. However, even
much shorter times often are sufficient for reaching close to steady
state, when the sample before has been kept in ambient light for
some time. The actinic light can be turned on/off either by the double
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