CHAPTER 4
SIMPLE EXPERIMENTS
(Y(II)) drops close to zero which is related to the dark idling state of
photosynthesis at which PS II electrons cannot be processed. The
subsequent activation of energy-consuming photosynthetic processes
recovers the PS II yield to intermediate values. Non-photochemical
quenching (blue symbols) is absent at start of actinic illumination be-
cause a trans-membrane
Δ
pH is absent. Ongoing illumination build-
up the
Δ
pH and, hence non-photochemical quenching. Towards the
end of illumination, part of the
Δ
pH is dissipated via the chloroplast
ATP synthase in response to the growing ATP requirements of carbon
fixation.
-
Switching off actinic illumination shuts down PS II photochemical
rates ensuing reoxidation of the intersystem electron transport and
recovery to initial values of the PS II photochemical yield. In paral-
lel, the trans-membrane
Δ
pH decays and non-photochemical quench-
ing drops.
-
Note that of fluorescence induction and recovery curves can be per-
formed automatically using the <IC+Recov.> command available in
the <Program> field.
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