Polygalacturonase Activity and Ethylene Synthesis during Cucumber Fruit Development and Maturation.

Polygalacturonase (EC 3.2.1.15) activity in seed cavity tissue from harvested cucumber fruit increased over 20-fold after the fruit had produced a transient burst of ethylene during maturation. This increase was observed in six cucumber cultivars and was present whether polygalacturonase activity was measured at pH 4.6 or 6.2. The seed cavity tissue pH decreased as polygalacturonase activity increased both in ripening fruit and in harvested immature fruit exposed to 10 microliters per liter ethylene in air.