CHANGES IN CELL-WALL POLYSACCHARIDES DURING THE GROWTH OF PHASEOLUS-VULGARIS LEAVES

The changes in pectic and hemicellulosic polysaccharides, and alpha-cellulose during the expansion growth of the primary leaves of Phaseolus vulgaris L. var. Pinta have been studied. alpha-Cellulose increased continuously with age, while pectic and water-soluble hemicellulose extracted with 4% KOH fractions slightly decreased. The water-soluble hemicelluloses extracted with 24% KOH showed the most conspicuous changes, increasing until the 8th day, when the absolute growth rate was maximal, and thereafter decreasing. Furthermore, the study of the molecular mass distribution of pectin, and water-soluble polysaccharides extracted with 4% and 24% KOH, showed an increase in the degree of polymerization of polyuronic acid and xylan, and an important depolymerization of galactan and xyloglucan. Accordingly, the mechanism of cell wall loosening in the leaf cell walls is similar to that described for plant axes.