Ultrastructural and Elementary Analyses of Silica-bodies in Epidermal Silica and Long Cells of the 2nd Leaves of Rice (Oryza sativa L.)

Abstract

Silica-bodies of Gramineae plants that are found in soil and in remains originate from and have species-specific forms. They give important information for the identification of fossil grass species. However, it has not been clear where the silica-bodies were formed in the plant cells. In this study, the high-pressure fixing method was applied to the transmission electron microscopy (TEM) of silica cells and long cells of rice, Oryza sativa L. Study of the silica cells in the epidermis of 2nd leaves revealed that electron-dense particles accumulate in the basal region of the cuticles, in the secondary cell walls, and in the cytoplasms, but not in the primary cell walls. In long cells with no secondary cell walls, electron-dense particles precipitated not only in the basal region of cuticles and the outer layers of the primary cell walls (outer and middle layers) but also in vacuoles. The EF-TEM studies revealed that the particles are composed of oxidized Si (SiO₂). Therefore, it can be concluded that in leaf tissue of rice the SiO₂-particles are fundamental components of the silica-bodies. The different distribution of the SiO₂-particles in silica cells and long cells may suggest that the mechanism of particle accumulation is different in these cells.