Silica-containing inclusions in the cytoplasm of diatom Synedra acus

Abstract

Cells of the araphid pennate diatom Synedra acus subsp. radians contain large inclusion (1–15 μm) storing silica, as revealed by transmission electron microscopy and EDX-analysis. The size of the inclusions increases with the time of cultivation of diatoms. Approximate concentration of SiO₂ in the inclusions is 1–4%. It is assumed that silica in the inclusions is present as gelatinized silica-gel. These results explain the possible mechanism of transport of silicic acid into the cell against the concentration gradient.