title: Whole-tissue determination of the rate coefficients of photoinactivation and repair of photosystem II in cotton leaf discs based on flash-induced P700 redox kinetics.
abstract: Using radioactively labelled amino acids to investigate repair of photoinactivated photosystem II (PS II) gives only a relative rate of repair, while using chlorophyll fluorescence parameters yields a repair rate coefficient for an undefined, variable location within the leaf tissue. Here, we report on a whole-tissue determination of the rate coefficient of photoinactivation k i , and that of repair k r in cotton leaf discs. The method assays functional PS II via a P700 kinetics area associated with PS I, as induced by a single-turnover, saturating flash superimposed on continuous background far-red light. The P700 kinetics area, directly proportional to the oxygen yield per single-turnover, saturating flash, was used to obtain both k i and k r . The value of k i , directly proportional to irradiance, was slightly higher when CO2 diffusion into the abaxial surface (richer in stomata) was blocked by contact with water. The value of k r , sizable in darkness, changed in the light depending on which surface was blocked by contact with water. When the abaxial surface was blocked, k r first peaked at moderate irradiance and then decreased at high irradiance. When the adaxial surface was blocked, k r first increased at low irradiance, then plateaued, before increasing markedly at high irradiance. At the highest irradiance, k r differed by an order of magnitude between the two orientations, attributable to different extents of oxidative stress affecting repair (Nishiyama et al., EMBO J 20: 5587-5594, 2001). The method is a whole-tissue, convenient determination of the rate coefficient of photoinactivation k i and that of repair k r .
authors.affiliation: The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, People's Republic of China.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Hu
authors.forename: Da-Yong
authors.initials: DY
authors.lastname: Fan
authors.forename: Pasquale
authors.initials: P
authors.lastname: Losciale
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
authors.forename: Wang-Feng
authors.initials: WF
authors.lastname: Zhang
mesh_terms: D000388:Air; D002244:Carbon / Q000378:metabolism; D003624:Darkness; D004579:Electron Transport / Q000528:radiation effects; D003368:Gossypium / Q000378:metabolism* / Q000528:radiation effects*; D007700:Kinetics; D008027:Light; D008034:Lincomycin / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D010100:Oxygen / Q000378:metabolism; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism* / Q000528:radiation effects*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002244:Carbon; D008034:Lincomycin; D010100:Oxygen