A marked reduction in staining intensity of cell wall material occurred predominantly in the treated kiwifruit tissues and might be partially accounted for by wall expansion. The loss of staining could be due to artifactual losses of cell wall material during sample preparation, but electron micrographs support the idea that loss of staining intensity reflects a change in cell wall structure and composition in situ, since it has not been revealed in the raw fruits. Thus either the material was being lost from the cell wall or there occurred chemical modifications, which reduced the reactivity of cell wall materials with the stain. Hemicellulose stains strongly, and it could be that during the OD there was a modification of hemicelluloses molecular size. This change might contribute to a decrease reactivity of hemicelluloses for staining by reducing the number of available staining sites (Redgwell, Melton,& Brasch, 1989, 1991).