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Chlorophyll Fluorescence

R.G. Walters mbrgw at s-crim1.dl.ac.uk
Wed May 3 05:27:20 EST 1995

(Halford Dace) writes:
>I have recently been doing some reading about chloroplast antioxidant
>mechanisms and am uncertain about some aspects of the generally
>accepted results of fluoresecence measurements.
>Reviews such as [1] and [2] listed below describe two types of fluorescence
>Qp (Photochemical quenching) which I understand as the quenching due to
>normal operation of the electron transport chain (ie reduction & reoxidation
>of Qa)

(should be qP)

>Qnp (nonphotochemical quenching) which they attribute largely to a quantity
>termed Qe (energy-dependant quenching), described as a transmembrane
>delta-pH dependent quenching.  In other words, as the thylakoid lumen [H+]
>increases, flourescence drops for reasons which I'm not clear about.

Should be "qN" - the terminology was revised in 1990, but people are still
not consistent in their usage.

qE is due to energy dissipation in the light harvesting apparatus, induced
by the delta-pH.  The most recent review is

"Regulation of Light Harvesting in Green Plants"
Horton P, Ruban AV, Walters RG (1994), Plant Physiol 106:415-420

Robin Walters,                              Robert Hill Institute, Sheffield UK
Scientists for Labour                                    R.G.Walters at shef.ac.uk
http://www.shef.ac.uk/uni/projects/sfl/index.html         mbrgw at seqnet.dl.ac.uk

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