Wall-softening enzymes in the gynoecium and pollen of Hemerocallis fulva

Abstract

Variations in extractable cellulase and pectinase were followed during development of Hemerocallis (day lily) flowers. A peak in cellulase activity occurs in the pistil just prior to anthesis, followed by a 62% diminution in the enzyme activity at the time of anthesis. Cellulase activity, per mg protein, is about twice as high in the upper (stigma) portion as in the middle and lower one-third of the pistil tissues. No pectinase activity was detected in the pistil at all stages of development. Extractable pectinase is present at a maximum level in the very young ovary; it decreases rapidly as the ovary develops. Cellulase remains at a moderate level of activity throughout the development of the ovary, except for an increase of about 50% at pollination. Soluble cellulase and pectinase are found in mature pollen. The changes in the cell-wall hydrolytic enzymes in the pistil were pollen-tube growth. It may also promote changes in the cell walls of the pistil cells, although metabolism of the middle lamella during pollen germination is primarily controlled by pollen pectinases.