CHAPTER 8 COMPONENTS OF THE MINI-PAM
reflecting, sealed window. In addition, for standard applications a
short-pass filter (λ<700 nm) is provided, which is mounted directly
on the lamp. This filter passes almost all visible light and only
eliminates the long wavelength radiation, against which the
fluorescence detector is not protected. For special applications, other
filters (e. g. daylight or blue) are available with which, however, the
maximal possible intensities are lower.
The External Halogen Lamp 2050-HB is meant to be used in
conjunction with PAR-measurements, as performed with the Leaf-
Clip Holder 2030-B. In its normal application, it is mounted on the
Leaf-Clip Holder, with the light (8° beam divergence angle) shining
at an approx. 60° incident angle with respect to the leaf plane on the
site where fluorescence and PAR are measured. The optimum angle,
giving maximal PAR and minimal shading by the fiberoptics can be
manually adjusted, preferentially using a white piece of paper instead
of a leaf. With the 15-turn potentiometer defined PAR-values can be
chosen, which are read off the MINI-PAM LC-display. A switch is
provided to turn the lamp on/off.
A major application of the External Halogen Lamp 2050-HB is
the adjustment of defined light intensities for measurements of light
saturation curves under field conditions. For this purpose, the light
obtained from this lamp may substitute or complement the natural
daylight. Intensities corresponding to PAR-values of more than 3000
µmol quanta m
-2
s
-1
can be achieved, exceeding the intensity of direct
sun light. Hence, this light source can be also useful for
photoinhibitory treatment of leaves and of other photosynthesising
organisms in the field. It should be noted that application of such
high light intensities will cause a substantial rise of leaf-temperature,
which is monitored by the thermosensor integrated in the Leaf-Clip
Holder 2030-B and can be read off the LC-display of the MINI-
PAM.
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