INVOLVEMENT OF CELL-WALL MATRIX IN LOW-TEMPERATURE ACCLIMATION OF WINTER-WHEAT

Alterations in the composition of root cell walls in winter wheat (Tri ticum aestivum L.) were studied during acclimation to chilling tempera tures. Chilling temperature (2 degrees C) was shown to induce transien t retardation of growth and a decrease in the content of matrix polysa ccharides in the root cell walls. The decrease in the incorporation of label from C-14-glucose into all fractions of cell-wall polysaccharid es reached the minimal value by the sixth hour of hypothermia. At the same time, transient activation of such enzymes as beta-fucosidase, be ta-glucosidase, and beta-cellobiosidase was observed. After one-day ex posure, the rate of label incorporation remained low for cellulose, wa s restored for pectins, and significantly increased for hemicelluloses . The most pronounced changes in monosaccharide composition and their binding types were found in the hemicellulose fraction (an increase in the content of t-Ara, 2-Ara, 4-Xyl, 3-Gal, and decrease in 6-Gal, 4-G lu, 4,6-Xyl, 3,4,6-Man). This indicates a decrease in the content of b ranched glucuronarabinoxylans and the glucanes of mixed composition. T he results showed the reactivity of the cell-wall matrix and the invol vement of the cell-wall metabolism (both anabolic and catabolic proces ses) in the adaptive response of the plant to low-temperature stress. It is supposed that these alterations are related to an increase in th e hardness of the cell wall.