ИСТИНА

The long-distance interactions of chloroplasts, mediated by lateral transport of molecules with the streaming cytoplasm, as well as the role of these interactions in regulation of pho- tosynthesis and plasmalemmal transport systems remained hidden for a long time. We applied a comparatively new approach to investigate the role of cyclosis in signal transmis- sion along large cells, such as internodes of characean algae. Microscopic measurements of chlorophyll fluorescence (F'm and F')in Chara corallina were performed on cell regions positioned few millimeters downstream from the zone of localized illumination under conditions of uninterrupted and transiently arrested cytoplasmic flow. When the temporal arrest of cytoplasmic streaming triggered by the action potential was concurrent with the incidence of localized illumination, the propagation of photoi nduced signal was postponed and decelerated, while the cytoplasmic level of the effector agent was lowered. Depending on the exact timing of localized illumination and streaming cessation, kinetics of the F' fluorescence response was characterized by positive or negative skewness. The results are significant for subsequent studies on regulatory and protective roles of cytoplasmic streaming in photosynthesizing plant cells