title: Reduction of the primary donor P700 of photosystem I during steady-state photosynthesis under low light in Arabidopsis.
abstract: During steady-state photosynthesis in low-light, 830-nm absorption (A(830)) by leaves was close to that in darkness in Arabidopsis, indicating that the primary donor P700 in the reaction center of photosystem I (PSI) was in reduced form. However, P700 was not fully oxidized by a saturating light pulse, suggesting the presence of a population of PSI centers with reduced P700 that remains thermodynamically stable during the application of the saturating light pulse (i.e., reduced-inactive P700). To substantiate this, the effects of methyl viologen (MV) and far-red light on P700 oxidation by the saturating light pulse were analyzed, and the cumulative effects of repetitive application of the saturating light pulse on photosynthesis were analyzed using a mutant crr2-2 with impaired PSI cyclic electron flow. We concluded that the reduced-inactive P700 in low-light as revealed by saturating light pulse indicates limitations of electron flow at the PSI acceptor side.
authors.affiliation: Department of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan. mtsuyama@agr.kyushu-u.ac.jp
authors.forename: Michito
authors.initials: M
authors.lastname: Tsuyama
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Kobayashi
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D002734:Chlorophyll / Q000378:metabolism*; D004583:Electrons; D008027:Light; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D010100:Oxygen; D010269:Paraquat / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects*; D045331:Photosystem I Protein Complex / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700; D010269:Paraquat; D010100:Oxygen