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CHAPTER 12
prefer to evaluate statistical aspects of the data at a later stage,
applying standard programs. The optional WinControl software also
allows averaging of stored data in a most comfortable way.
Another case where averaging is advantageous relates to
measurements under extreme environmental conditions which cause
almost complete loss of variable fluorescence, i.e. when YIELD
approaches zero, while ETR may still be substantial due to high
PAR-values. Under such conditions, even the MINI-PAM becomes
limited by the signal/noise ratio in YIELD-determination, which can
be improved by averaging.
Before use of the averaging function, the SET-key must be
pressed in menu position 11 and AV. YIELD RESET must be
confirmed by pressing the ∧-key. Then with every application of a
saturation pulse the measured values of YIELD (Y) and ETR (E) will
be averaged until another reset is carried out.
12.3.11 INDUCTION CURVE (menu point 21) and
INDUCTION CURVE+RECOVERY (menu point 22)
Dark/light induction curves (Kautsky effect) contain complex
information on the photosynthetic performance of a plant at different
functional levels (see 12.1). By repetitive application of saturating
light pulses and quenching analysis additional information is
obtained which is essential for reliable interpretation of the Kautsky
effect. After a longer period of darkness, Calvin-cycle enzymes are
partially inactivated. They are light-activated during the first minutes
of illumination. During this induction period oxygen instead of CO
serves as terminal electron acceptor. O
(Mehler-Ascorbate-Peroxidase Cycle) as well as cyclic electron flow
at photosystem I create a large proton gradient, which will be used
for ATP-synthesis only after Calvin cycle has been light activated.
MEASUREMENTS WITH THE MINI-PAM
dependent electron flow
2
2
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