SILICA DEPOSITION AND ULTRASTRUCTURE IN THE CELL-WALL OF EQUISETUM-ARVENSE - THE IMPORTANCE OF CELL-WALL STRUCTURES AND FLOW-CONTROL IN BIOSILICIFICATION

Scanning and transmission electron microscopy have been used in the investigation of the surface micromorphology and ultrastructure of silicas extracted from different regions of the horsetail Equisetum arvense. The surface micromorphology was found to be very complex and varied with the anatomical region of the plant. Principally fibrillar, globular and sheet-like ultrastructural motifs of silica were observed, their proportions and detailed structure also varying with the anatomical region studied. The physiocochemical mechanisms by which these structural motifs arise are discussed in relation to the surface micromorphologies observed and to their anatomical function.