Changes in amounts and molecular mass distribution of cell-wall polysaccharides of wheat (Triticum aestivum L) coleoptiles under water stress

Polyethylene glycol (PEG)-induced water stress suppressed growth of wheat (Triticum aestivum L.) coleoptiles. When PEG was removed, the growth rate of coleoptiles rapidly increased, and the length reached the same level as that of the unstressed coleoptiles. The amounts of cell-wall polysaccharides, such as hemicellulose and cellulose, per coleoptile increased under unstressed conditions as coleoptiles grew The suppression of growth by water stress led to the reduction of the increases in the amounts of hemicellulose and cellulose. In response to the PEG removal, the increases in cell-wall polysaccharides recovered, and the amounts became close to those of unstressed coleoptiles. A close correlation was observed between the amounts of hemicellulose and cellulose and the length of coleoptiles. These results indicate that coleoptile cells keep their ability to grow even under water-stress conditions, and that cellulose and hemicellulose are produced in parallel with the cell elongation. The gel permeation chromatography of the hemicellulose fraction showed that PEG treatment reduced the increases in the amounts of middle and low molecular-mass polysaccharides. However, the increases in high molecular-mass polysaccharides, such as beta-glucans and arabinoxylans, were not affected by the suppression of growth. The synthesis of high molecular-mass portion of hemicellulosic polysaccharides seems to be related to preserving the ability of the cell walls to extend rather than to cell elongation.