Changes in the autolytic activities of maize coleoptile cell walls during coleoptile growth
Inouhe, M. (Ehime Univ., Matsuyama (Japan). Faculty of Science) | Nevins, D.J.
Autolytic activities of coleoptile cell walls were measured in developing maize seedlings. The major neutral sugar components of the cell wall polysaccharides were arabinose, xylose and glucose. The quantities of all these components per coleoptile increased for 5 d after germination, suggesting that levels are augmented by biosynthetic processes during coleoptile growth. However, cell wall preparations isolated from the coleoptile also revealed increasing rates of autolytic activity directed toward each of the sugar components. This result suggests that the constitutive hydrolytic activities expressed by cell walls also increase as a function of coleoptile age. The proportion of glucose in autolysis products relative to that present in the cell walls specifically increased with coleoptile age, while the ratios for arabinose and xylose decreased. Kinetic analyses of autolysis demonstrated that the reactions specific for pentoses at the early growth stage are transient events and that initial low rates of glucan autolysis increased sharply and persisted longer. In these expedients the products of glucan autolysis were largely monomeric while those of the pentose-specific reactions consisted of both monomeric and polymeric sugars. Based on these results, we concluded that two distinct phases of autolytic activities are expressed in the mediation of cell wall polysaccharide metabolism in situ
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