THE MORPHOLOGY AND ANATOMY OF CALLIPTERIDIUM SULLIVANTI

JENSEN, WILLIAM A. (U. California, Berkeley.) The composition of the developing primary wall in onion root tip cells. II. Cytochemical localization. Amer. Jour. Bot. 47(4): 287-295. Illus. 1960.-The composition of the developing cell wall in the first 2 mm. of the onion root tip was studied using a cytochemical technique that permitted the detection of hemicellulose and the noncellulosic polysaccharides as well as the pectic substances and cellulose. The technique is based on the combination of a differential extraction procedure with the periodic acid-Schiff reaction for carbohydrates. The data obtained indicate that the cells of the apical initials are low in all wall substances but that all of the wall materials are present to some extent. Early in cell development, differences appear in the composition of the walls of the various tissues. The cortical cells are relatively high in the noncellulosic polysaccharides and cellulose while relatively low in the pectic substances and hemicellulose. Very early in development the protoderm is similar to the cortex, but differences develop during the radial enlargement of the cells. During this stage the walls of the protodermal cells are low in the noncellulosic polysaccharides and cellulose and high in pectic substances and hemicellulose. As elongation progresses, these differences are lost and the 2 tissues become very similar. The vascular cell walls are low in the noncellulosic polysaccharides and cellulose and are high in pectic substances and hemicellulose early in development. Later, hemicellulose becomes relatively more important. When the cell wall materials are sequentially extracted, no change in the general morphology of the cell occurs until only the noncellulosic polysaccharides and the cellulose remained. When the noncelluilosic polysaccharides are then removed, the cells remain intact but are 30% less in diameter. This suggests that while cellulose is of critical importance, the noncellulosic polysaccharides may play a major role in determining the physical characteristics of the wall. THERE are 2 methods of approach available for studies of the composition of the developing primary cell wall in the root tip. They are: (1) the quantitative analysis of segments of the root using biochemical procedures and (2) the cytochemical localization of the various components in the developing wall. The first paper in this series, (Jensen and Ashton, 1 Received for publication August 11, 1959. Research supported by grant G-4286 of the National Science Foundation. The author wishes to thank Dr. Melvin Fuller and Mr. Patrick Healey for aid in the photomicrography. 1960), contains the results of microchemical analyses of the first 20 consecutive lOO,u-sections of the onion root tip. The data obtained from the analysis of each section are expressed on a per cell basis by dividing the amount per section by the number of cells in that section. Thus, changes in the wall of the developing cell can be studied by comparing the data from the various sections, but differences between various types of cells in the same section are not seen. The second method of approach overcomes this last difficulty by actually making visible, by cytochemical reactions, the various cell wall compo. This content downloaded from 157.55.39.186 on Sun, 09 Oct 2016 05:40:53 UTC All use subject to http://about.jstor.org/terms