Propagation of photoinduced signals with the cytoplasmic flow along Characean internodes: evidence from changes in chloroplast fluorescence and surface pHстатья
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Дата последнего поиска статьи во внешних источниках: 19 июля 2013 г.
Аннотация: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 brightly illuminated 400-µm wide zone elevated the maximal fluorescence Fm' in the analyzed downstream area, whereas at higher background irradiances it induced strong quenching of Fm'. At intermediate irradiances the increase and decrease in Fm' appeared as two successive waves. The transition between the Fm' 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 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 from the concurrent alkaline pH shift on the cell surface. It is proposed that the initial increase in Fm' after application of a distant photostimulus is determined, among other factors, by the wave of alkaline cytoplasmic pH.