Plant & Cell Physiol. 20(6): 1117-1124 (1979) Growth and cell wall changes in rice coleoptiles growing under different conditions I. Changes in turgor pressure and cell wall polysaccharides during intact growth Ignacio Zarra 1 and Yoshio Masuda 2 Department of Biology, Faculty of Science, Osaka City University, Sumiyoshi-ku, Sugimoto-cho, Osaka 558, Japan (Received May 21, 1979) The effect of the oxygen supply on growth, water absorption of cells and cell wall changes was studied in coleoptiles of rice seedlings growing under three different con- ditions: under water, under water with constant air bubbling and in air. Coleoptile growth was larger when they were grown under water than in water with air bubbling and in air. Coleoptile growth under water was limited by the suction force of their cells rather than by mechanical properties of the cell wall, while that of the coleoptiles growing under the other two conditions was limited by the cell wall rigidity. A decrease in the relative amount of noncellulosic glucose of the cell wall, and an increase in the non- cellulosic xylose during coleoptile growth were found for all three culture conditions. Key words: Cell wall — Noncellulosic polysaccharides — Rice seedlings — Turgor pressure. Cell elongation is primarily controlled by two factors (3, 10): turgor pressure, acting as the driving force for cell extension and wall loosening. Cell wall loosening, or the capacity of the cell wall to extend, has been demonstrated to be represented by the decrease in the minimum stress-relaxation time (T o value) measured by the stress-relaxation technique (9, 19-22). As to the biochemical modifications underly- ing cell wall loosening, much attention has been paid to the changes in noncellulosic polysaccharides of the cell wall (2, 7, 11, 24). In some dicots and corn seedlings (//) and in oat coleoptiles (15), a glucose-containing polymer is the predominant non- cellulosic polysaccharide of the cell wall prior to elongation and rapidly decreases during the early stages of elongation, while the xylose content increased at the same time (11). Sakurai and Masuda (17, 18) also found that the amount of noncellulosic glucose of barley coleoptile cell wall decreases with coleoptile age and that the growth capacity of the coleoptile segments in response to auxin is related to the amount of noncellulosic glucose present in the cell wall. On the other hand, in intact azuki bean stems (Vigna angularis), a correlation between the amount of noncellulosic galactan and growth capacity has been found (13). Abbreviations: IAA, Indole-3-acetic acid; T 0) minimum stress-relaxation time. 1 Present address: Departamento de Fisiologia Vegetal, Facultad de Ciencias, Universidad, Sala- manca, Spain. 2 To whom reprints should be requested. 1117