Calcium in pollen-pistil interaction in Petunia hybrida Hort. III. Localization of Ca2+ ions and Ca(2+)-ATPase in pollinated pistil.

Studies were carried out of CA2+ and CA(2+)-ATPase localization in pollinated (6 and 48 h after pollination) pistils of Petunia hybrida. The results were confronted with CA2+ localization in mature pollen grain and in unpollinated pistil. It has been found that after pollination the number of CA2+ sequestered in the stigmal exudate and in the sporoderm of the pollen grain gets lower. That phenomenon was associated with the appearance of a large number of Sb/Ca precipitates in the submembrane cytoplasm of the germinating pollen. In the vacuolized pollen grain, i.e. grown into a pollen tube, there were only a few precipitates. In the pollen tube, CA2+ were found in the organelles of the tip cytoplasm and in the external pectin cell wall. Studies with the use of 45Ca2+ have revealed that the source of calcium ions incorporated into the pollen tube tip and its pectin wall is the transmitting tract of the style. In the transmitting tract overgrown with pollen tubes, Ca2+ were located in the intercellular matrix and in the transmitting cells. Sb/Ca precipitates occurred in the nuclei, around the secretory vesicles and on the plasmalemma in the transverse walls region. Elevated Ca2+ level was found in degenerating cells (inhibited pollen tubes, transmitting cells, nucellar cells). The progressing degeneration process of the cells of the transmitting tract of the pollinated pistil was associated with a decrease in the activity of plasmalemmal Ca(2+)-ATPase.