Methods for visualizing cell wall texture

Different methods for visualizing cell wall texture are compared; (1) thin-sectioning and staining with potassium permanganate after removal of the cell wall matrix, (2) thin sectioning and on-block staining with uranyl acetate during freeze-substitution, (3) freezefracturing of untreated material, and (4) shadow-casting after drycleaving of material from which the wall matrix had been removed. Sections mainly give information on the type of texture. The other methods, being surface preparations, yield a clearer picture of the constituent elements, the microfibrils. Thin sections of material fixed in glutaraldehyde and osmium tetroxide and stained on the grid with uranyl acetate and lead citrate proved to be unreliable for determining cell wall texture. The meandering of microfibrils in dry-cleaved and shadow-casted preparations is supposed to be an artefact of this method. It is supposed that the actual width of the crystalline core of the cellulose microfibril is 3-6 + 1 -9 nm, as measured from sections stained with potassium permanganate of material treated with hydrogen peroxide/glacial acetic acid.