Polysaccharide Synthesis and Turnover in the Cell Walls of Growing and Non-growing Cells of Gravistimulated Sunflower Hypocotyls.

No significant changes were detected in the proportions of the various monosaccharides present in the cell wall polysaccharides of the peripheral cell layers on the upper and lower sides of sunflower hypocotyls which had undergone gravicurvature. The incorporation of radioactive glucose into the major classes of polysaccharide was similar in the walls of growing (convex) and non-growing (concave) cells. Autoradiographic studies showed that most of the newly incorporated material was located in the innermost layers of the cell wall, this being the case at both the upper and lower sides of the curving hypocotyl. During the period of differential growth causing curvature, the turnover of the recently incorporated glucose was not detected. These results may mean that neither the relative rates of synthesis of the main polysaccharides nor the turnover of recently incorporated major polysaccharides were influenced significantly by short term changes in growth rate of the peripheral cell layers.