daceh at shrike.und.ac.za
Wed May 3 02:35:29 EST 1995
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  and  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
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.
Can anybody enlighten me on the mechanism of Qe? I'd really appreciate either
an explanation or a pointer to some reference.
 Krause, G.H. (1988) Photoinhibition of photosynthesis. An evaluation of
damaging and protective mechanisms. Physiologia Plantarum 74: 566-574
 Foyer, C.H., Lelandais, M. and Kunert, K.J. (1994) Photooxidative stress
in plants. Physiologia Plantarum 92: 696-717
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