Localization of insoluble and pectic polysaccharides in particular ovary regions in sour cherry (Prunus cerasus L.) was studied at full bloom. In the period of intensive pollen tube growth through the transition zone be¬tween pericarp and style, this zone stains intensively for pectic polysaccharides. In the cells of the obturator and the placenta, small starch grains are present in both pollinated and unpollinated flowers. In the primary ovule, in which fertilization takes a normal course, large starch grains are present in the integumentary cells, with the highest concentration in the micropylar region. After pollen tube penetration through the micropyle, the cytoplasm of the integument cells show¬ed a PAS-positive reaction.
The embryo sac contains only small starch grains, occurring sporadically in the synergid cytoplasm and the central cell, with the peak concentration in the egg cell. It has been observed that in both pollinated and unpollinated flowers, there is a pronounced tendency for starch grains to accumulate in the described parts of the ovule from day 2 to day 4 of full bloom. In the unpollinated ovules, starch grain hydrolysis is much quicker than in the pollinated ones. Concurrently with this process, they lose their normal histological struc¬ture showing intense positive reaction of their walls to pectic polysaccharides. Starch grains are present in the embryo only in the early stages of embryogenesis.
Localization and distribution of insoluble and pectic polysaccharides, as well as their interrelationship, in the sour cherry are closely linked to their role in the pro¬cesses of fertilization and early embryogenesis occur¬ring in the ovary at full bloom.