Distribution of Charasomes in Chara: Banding Pattern and Effect of Photosynthetic Inhibitors

Abstract

Charasomes are structured elaborations of plasmalemma of some Charophytes which may be involved in enhanced transport of ions or inorganic carbon across the plasmalemma. They show a highly non-uniform distribution. We report here a novel method of quantifying charasome population density, using scanning electron microscopy of cell fragments removed from the cell wall. Consistent differences in density can occur in neighbouring regions of the membrane. The distribution of densities is not normal, but is skewed toward lower densities, with large areas of membrane showing no charasomes. Contrary to previous published reports, we found no correlation with acid and alkaline banding patterns. Inhibition of photosynthesis by either dark or DCMU (dichlorophenyl dimethyl urea, an inhibitor of photosystem II) results in a complete loss of charasomes in 1-3 weeks.