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The fluorescence signal continues to drop as full activation of rubisco continues and state
transitions occur. Full activation of rubisco in both algae and higher plants takes between
three to four minutes plus intensity values are driven down by non-photochemical quenching.
Nonphotochemical quenching is involved in photo-protection, state transitions, and
photoinhibition. The
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ph of the thylakoid lumen and the xanthophyll cycle take between two
to four minutes to adjust to a new light level (Lichtenthaler 1999). State transitions take
between fifteen and twenty minutes to adjusts to a light level, and therefore, steady state
photosynthesis takes between fifteen and twenty minutes (Maxwell and Johnson 2000). Under
photo inhibitory conditions, D1 protein degradation found in PSII reaction centers, close PSII
reaction centers. Other mechanisms have also been suggested for being involved in
photoinhibition.
It is common to take quenching measurements at steady state photosynthesis after the leaf has
fully adapted to a specific light level. However Klughammer claims that Y(NO) can be
measured at other times. Graphing quenching values at non steady state conditions as well as
at steady state can be done to understand the process. (MacIntyre, Sharkey, Geider 1997).