TY - JOUR
T1 - Novel effects of methyl viologen on photosystem II function in spinach leaves
AU - Fan, Da Yong
AU - Jia, Husen
AU - Barber, James
AU - Chow, Wah Soon
PY - 2009/1
Y1 - 2009/1
N2 - Methyl viologen (MV) is a well-known electron mediator that works on the acceptor side of photosystem I. We investigated the little-known, MV-induced inhibition of linear electron flow through photosystem II (PS II) in spinach-leaf discs. Even a low [MV] decreased the (1) average, light-adapted photochemical efficiency of PS II traps, (2) oxidation state of the primary quinone acceptor QA in PS II during illumination, (3) photochemical efficiency of light-adapted open PS II traps, (4) fraction of absorbed light energy dissipated constitutively in a light-independent manner or as chlorophyll (Chl) a fluorescence emission, (5) Chl a fluorescence yield corresponding to dark-adapted open reaction-center traps (F o) and closed reaction-center traps (F m), and (6) half-time for re-oxidation of Q A - in PS II after a single-turnover flash. These effects suggest that the presence of MV accelerates various "downhill" electron-transfer steps in PS II. Therefore, when using the MV to quantify cyclic electron flow, the inhibitory effect of MV on PS II should be taken into account.
AB - Methyl viologen (MV) is a well-known electron mediator that works on the acceptor side of photosystem I. We investigated the little-known, MV-induced inhibition of linear electron flow through photosystem II (PS II) in spinach-leaf discs. Even a low [MV] decreased the (1) average, light-adapted photochemical efficiency of PS II traps, (2) oxidation state of the primary quinone acceptor QA in PS II during illumination, (3) photochemical efficiency of light-adapted open PS II traps, (4) fraction of absorbed light energy dissipated constitutively in a light-independent manner or as chlorophyll (Chl) a fluorescence emission, (5) Chl a fluorescence yield corresponding to dark-adapted open reaction-center traps (F o) and closed reaction-center traps (F m), and (6) half-time for re-oxidation of Q A - in PS II after a single-turnover flash. These effects suggest that the presence of MV accelerates various "downhill" electron-transfer steps in PS II. Therefore, when using the MV to quantify cyclic electron flow, the inhibitory effect of MV on PS II should be taken into account.
KW - Cyclic electron flow
KW - Exciton-radical pair equilibrium
KW - Linear electron flow
KW - Methyl viologen
KW - Photosystem II
UR - http://www.scopus.com/inward/record.url?scp=70450235338&partnerID=8YFLogxK
U2 - 10.1007/s00249-009-0484-3
DO - 10.1007/s00249-009-0484-3
M3 - Article
SN - 0175-7571
VL - 39
SP - 191
EP - 199
JO - European Biophysics Journal
JF - European Biophysics Journal
IS - 1
ER -