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Influence of photoinhibition on electron transport and photophosphorylation of isolated chloroplasts
Author(s) -
Curwiel Victor B.,
Rensen Jack J. S.
Publication year - 1993
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1993.tb01791.x
Subject(s) - photophosphorylation , photoinhibition , thylakoid , chloroplast , electron transport chain , photosystem i , photosystem ii , biophysics , electrochemical gradient , hill reaction , biology , electron flow , botany , chemistry , photochemistry , photosynthesis , membrane , biochemistry , gene
The effects of a photoinhibition treatment (PIT) on electron transport and photophosphorylation reactions were measured in chloroplasts isolated from triazine‐resistant and susceptible Chenopodium album plants grown under high and low irradiance. Electron transport dependent on photosystem I (PSI) alone was much less affected by PIT than that dependent on both photosystem II (PSII) and PSI. There was a smaller difference in susceptibility to PIT between the photophosphorylation activitity dependent on PSI alone and that dependent on both PSII and PSI. Because in all cases photophosphorylation activity decreased faster upon PIT than the rate of electron transport, we conclude that photoinhibition causes a gradual uncoupling of electron transport with phosphorylation. Since the extent of the light‐induced proton gradient across the thylakoid membrane decreased upon PIT, it is suggested that photoinhibiton causes a proton leakiness of the membrane. We have found no significant differences to PIT of the various reactions measured in chloroplasts isolated from triazine‐resistant and susceptible plants. We have also not observed any significant differences to PIT of the photophosphorylation reactions in chloroplasts of plants grown under low irradiance, compared with those grown under high irradiance. However, the electron transport reactions in chloroplasts from plants grown under low irradiance appeared to be somewhat less sensitive to PIT than those grown under high irradiance.