Dark Leaf Clip Dlc-8 - Walz MINI-PAM Manual

CHAPTER 8
8.6

Dark Leaf Clip DLC-8

The Dark Leaf Clip DLC-8 weighs approx. 4 g and, hence, can
be attached to most types of leaves without any detrimental effects. It
is equipped with a miniature sliding shutter which prevents light
access to the leaf during a dark-adaptation period and which is
opened for the actual measurement only, when exposure to external
light is prevented by the fiberoptics. Proper dark-adaptation is
essential for determination of the maximal quantum yield Fv/Fm (see
12.3.1).
Different from the other leaf clips, with the Dark Leaf Clip
DLC-8 the fiberoptics are positioned at right angle with respect to
the leaf surface at the relatively short distance of 7 mm. As a
consequence, signal amplitudes are approx. 2-3 times higher than
with the Leaf-Clip Holder 2030-B. In order to avoid signal
saturation, the settings of MEAS-INT (menu point 50) and GAIN
(menu point 49) have to be correspondingly lowered with respect to
the standard settings. For optimal results the burst mode of
measuring light (menu position 5: ML-BURST) is recommended
(see 12.3.2).
When the shutter is still closed and measuring light is on, an
artifactual signal is observed, which is due to a small fraction of the
measuring light which after reflection from the closed shutter
penetrates to the photodetector. However, the reflection is much
smaller when the shutter is opened and the measuring light hits the
strongly absorbing leaf instead of the shiny metal. Therefore, it is
recommended to carry out compensation of the unavoidable
background signal by AUTO-ZERO (menu point 2) with the
fiberoptics end directed into the air.
COMPONENTS OF THE MINI-PAM
47