title: Propagation of photoinduced signals with the cytoplasmic flow along Characean internodes: evidence from changes in chloroplast fluorescence and surface pH.
abstract: Emerging evidence suggests that cytoplasmic streaming can regulate the plasma-membrane H(+) transport and photosynthetic electron flow. Microfluorometric and surface pH measurements on Chara corallina internodes revealed the transmission of photoinduced signals by the cytoplasmic flow for a distance of few millimeters from the site of stimulus application. When a 30-s pulse of bright light was locally applied, the downstream cell regions responded with either release or enhancement of non-photochemical quenching of chlorophyll fluorescence, depending on the background irradiance of the analyzed cell area. Under dim background irradiance (<20 μmol m(-2) s(-1)), the arrival of the distant signal from the brightly illuminated 400-μm-wide zone elevated the maximal fluorescence F m (') in the analyzed downstream area, whereas at higher background irradiances it induced strong quenching of F m (') . At intermediate irradiances the increase and decrease in F m (') appeared as two successive waves. The transition between the F m (') responses of opposite polarities occurred at a narrow threshold range of irradiances. This indicates that inevitable slight variations in irradiance at the bottom chloroplast layer combined with the cyclosis-transmitted signals may contribute to the formation of a photosynthetic activity pattern. The rapid cyclosis-mediated release of non-photochemical quenching, unlike the delayed response of opposite polarity, was associated with opening of H(+) (OH(-))-conducting plasma membrane channels, as evidenced by the concurrent alkaline pH shift on the cell surface. It is proposed that the initial increase in F m (') after application of a distant photostimulus is determined, among other factors, by the wave of alkaline cytoplasmic pH.
authors: Department of Biophysics, Faculty of Biology, Moscow State University, Moscow, 119991, Russia. bulychev@biophys.msu.ru
authors: Alexander A
authors: AA
authors: Bulychev
authors: Anna V
authors: AV
authors: Alova
authors: Andrey B
authors: AB
authors: Rubin
mesh_terms: D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D044784:Chara / Q000378:metabolism*; D002734:Chlorophyll / Q000737:chemistry; D002736:Chloroplasts / Q000737:chemistry*; D003571:Cytochalasin B / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism*; D005470:Fluorometry / Q000379:methods; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D008027:Light; D008856:Microscopy, Fluorescence / Q000379:methods; D017785:Photons; D011522:Protons
chemical_list: D011522:Protons; D002734:Chlorophyll; D003571:Cytochalasin B