THE INVERTASE OF THE CORN RADICLE AND ITS ACTIVITY IN SUCCESSIVE STAGES OF GROWTH

Abstract

Segments of the first 10 millimeters of corn radicle tips have been analyzed in terms of invertase activity, cell number, fresh and dry weights, and sugar content. Invertase activity per cell increased 40-fold as the meristematic cell advanced to the stage of most rapid elongation, and again subsided as the cell ceased to elongate and entered the stage of maturation. In the growing cell, the concentration of sucrose remained low while that of reducing sugars increased fivefold.The corn radicle invertase was found to be a β-fructofuranosidase with a K_m of 0.006 M and a pH optimum of 4.6. Kinetic studies indicate that there is no change in the nature of the corn radicle invertase during cell growth. Equivalent activities of intact cells or segments and homogenates is consistent with the assumption that the enzyme is located outside the permeability barrier of the cells.