title: Differential effects of plasma membrane electric excitation on H+ fluxes and photosynthesis in characean cells.
abstract: Cells of characean algae exposed to illumination arrange plasma-membrane H(+) fluxes and photosynthesis in coordinated spatial patterns (bands). This study reveals that H(+) transport and photosynthesis patterns in these excitable cells are affected not only by light conditions but also by electric excitation of the plasma membrane. It is shown that generation of action potential (AP) temporally eliminates alkaline bands, suppresses O(2) evolution, and differentially affects primary reactions of photosystem II (PSII) in different cell regions. The quantum yield of PSII electron transport decreased after AP in the alkaline but not in acidic cell regions. The effects of electric excitation on fluorescence and the PSII electron flow were most pronounced at light-limiting conditions. Evidence was obtained that the shift in chlorophyll fluorescence after AP is due to the increase in DeltapH at thylakoid membranes. It is concluded that the AP-triggered pathways affecting ion transport and photosynthetic energy conversion are linked but not identical.
authors.affiliation: Department of Biophysics, Faculty of Biology, Moscow State University, Moscow 119992, Russia. bulychev@biophys.msu.ru
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Bulychev
authors.forename: Natalia A
authors.initials: NA
authors.lastname: Kamzolkina
mesh_terms: D000200:Action Potentials / Q000502:physiology* / Q000528:radiation effects; D002462:Cell Membrane / Q000502:physiology*; D044522:Characeae / Q000502:physiology* / Q000528:radiation effects; D004056:Differential Threshold / Q000502:physiology; D004558:Electric Stimulation / Q000379:methods*; D004574:Electromagnetic Fields; D008027:Light; D008564:Membrane Potentials / Q000502:physiology* / Q000528:radiation effects; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D017494:Proton Pumps / Q000502:physiology / Q000528:radiation effects; D011522:Protons
chemical_list: D017494:Proton Pumps; D011522:Protons