Ultrastructure and microanalysis of silica bodies in Dactylis Glomerata L.

Silica bodies of orchard grass (Dactylis glomerata L.) were analysed by transmission electron microscopy and X-ray microanalysis. Silica bodies are inserted into the epidermis of the leaf and consist of a rather compact amorphous silica and low carbon. In particular regions of the interface between silica body and cell wall, silica is crossed by electron opaque strands, which are similar to filaments of the cell wall and most probably represent cellulose fibrils. The presence of a higher carbon content in this region than in the compact silica supports this notion. Cells with silicified walls or lumen were found apart from typical silica bodies. They most likely represent early or intermediate stages of silica body formation. Some epidermal cells showed silica deposits between protoplast and cell wall with small but regularly detected nitrogen and phosphorus peaks indicating a particular extracellular chemical composition probably involved in silica accumulation.