title: Cyclic electron flow around photosystem I is enhanced at low pH.
abstract: Earlier studies have shown that at low pH (pH 5.5), PS II fluorescence decreases with concomitant increase in PS I fluorescence (Singh-Rawal et al., 2010). In order to shed light on the reasons of the above stated change, spinach leaf discs were treated with buffers of different pH (7.5, 6.5 and 5.5)and decrease in the photochemical quantum yield of PS II,Y(II) and increase in the photochemical quantum yield of PS I,Y(I) was observed. We observed an enhanced protection against over-reduction of PS I acceptor side at low pH (5.5) treated leaves. This was obviously achieved by the rapid build-up of trans-thylakoid pH gradient at low light intensities and was directly associated with a steep increase in non- photochemical quenching of chlorophyll fluorescence and a decrease in the electron transport rate of PS II. Our results suggested a strong stimulation of cyclic electron flow around PS I at pH 5.5 which directly supports protection against over-reduction of the PS I acceptor side.
authors.affiliation: School of Life Science, Devi Ahilya University, Indore 452 017, M.P., India.
authors.forename: Teena
authors.initials: T
authors.lastname: Tongra
authors.affiliation: School of Life Science, Devi Ahilya University, Indore 452 017, M.P., India.
authors.forename: Sudhakar
authors.initials: S
authors.lastname: Bharti
authors.affiliation: School of Life Science, Devi Ahilya University, Indore 452 017, M.P., India. Electronic address: anjanajajoo@hotmail.com.
authors.forename: Anjana
authors.initials: A
authors.lastname: Jajoo
mesh_terms: D004579:Electron Transport / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*; D018724:Spinacia oleracea / Q000201:enzymology*
chemical_list: D045331:Photosystem I Protein Complex
keywords: Chlorophyll fluorescence; Cyclic electron flow; Electron transport rate; Energy dissipation; Photosystem I; Photosystem II; Quantum yield