CHAPTER 7 THE MODE-MENU
can be also directly started by double key operation ON + ∧. The
time periods at the different intensities are set by menu point 19: LC-
WIDTH. There is a blinking sign (LC) in the upper left corner of the
display while a LIGHT CURVE is recorded. The series involves
YIELD-determinations at 8 settings of actinic light. It starts with the
intensity-setting, which is selected by 20: LC-INT, where one can
choose between values from ACT-INT 1 to 5, with the standard
setting being ACT-INT 3. The range of absolute PAR-values
corresponding to these settings can be moved up and down with the
help of menu point 16: AL-FACT or by changing the distance
between fiberoptics and sample. The effective PAR-values at the
sample surface may be calibrated by the LIGHT-CALIBRATION
routine (menu point 8). A LIGHT CURVE can provide profound
information on the overall photosynthetic performance of a plant,
even if the illumination periods are too short to achieve true steady
states. Note: Due to the unavoidable internal heating during
recording of a LIGHT CURVE, assessment of absolute
fluorescence
signal amplitudes is problematic, but this does not
affect correct
determination of the ratio ∆F/Fm'.
When switched on via SET, a LIGHT
CURVE is measured as described for menu
point 17 and in the following dark period the recovery of YIELD is
assessed by 6 consecutive measurements at 10 s, 30 s, 60 s, 2 min,
5 min and 10 min following illumination. Note: Due to the
unavoidable internal heating during recording of a LIGHT CURVE
assessment of absolute
fluorescence signal amplitudes is
problematic, but this does not
affect correct determination of the ratio
∆F/Fm'.
18:L.CURVE+REC:OFF(SET)
F: 448 745Y 6.2E 20L
LC-WIDTH determines the illumination
time at each intensity setting. 10 s are
19: LC-WIDTH 0:10 (SET)
F: 448 745Y 6.2E 20L
21
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