Correlative Studies of Cell Wall Enzymes and Growth

If cell wall hydrolytic enzymes are involved in extension growth, a correlation may be expected between hydrolytic activity of the cell walls and growth rate of the tissue from which the walls are prepared. Epicotyl sections from 0 to 5 mm, 6 to 10 mm, and 11 to 15 mm below the apical hook of pea seedlings (Pisum sativum var. Alaska) have relative growth rates of 100:15:2, respectively. The relative beta-glucosidase activities (units/mg wall) of cell walls from these sections are respectively, 100:24:23, for walls prepared in glycerol and 100:42:23 for walls prepared in aqueous solution. Thus, there is a correlation between growth rate of the tissue and specific activity of the wall-associated beta-glucosidase. Similar correlations were found for other cell wall-associated hydrolases.Relative cell numbers for the above sections, as determined by counting, were 100:25:16, and with these data it could be calculated that the amount of cell wall beta-glucosidase activity per cell is essentially a constant. Thus, for epicotyl sections the amount of enzyme per cell does not change during the process of cell elongation but the specific activity declines as the result of deposition of new wall material.