The Significance of the Obturator in the Control of Pollen Tube Entry into the Ovary in Peach (Prunus persica)

Changes in the obturator of the peach (Prunus persica) have been investigated and related to pollen tube growth in this region. At anthesis, the cells of the obturator are active and rich in starch reserves. Twelve days after anthesis these cells produce a secretion that stains for carbohydrates and for proteins. As the secretion is produced, starch vanishes from these cells and they degenerate and collapse as callose is accumulated. Secretion is independent of pollination as it takes place in a similar fashion both in pollinated and in unpollinated flowers. Pollen tube growth along the obturator surface depends on this secretion for, although pollen tubes reach the base of the style seven days after pollination, they cannot grow on the obturator until five days later, when the secretion is produced. This discontinuous secretion taking place at the obturator may provide a mechanism that controls the entrance of pollen tubes into the ovary in the peach.