Localization of membrane-associated calcium in unpollinated and pollinated pistil of Petunia hybrida Hort.

Abstract

In the pistil of Petunia hybrida, the transmitting tract and the ovules are the sites which give Ca²⁺-CTC fluorescence. In unpollinated pistil the level of membrane-associated Ca²⁺ decreases from the stigma to the base of the style. The renewed strong rise of Ca²⁺-CTC fluorescence appears on the placenta surface and in the ovule integuments. Following pollination, when the pollen tubes have grown through the pistil, the pattern of membrane-associated Ca²⁺ on the path stigma - ovary is reversed. The highest fluorescence is found in the base of the style. In pollinated ovules the Ca²⁺-CTC fluorescence increases markedly. In the transmitting cells membrane-associated Ca²⁺ occurs mainly in the polar regions of the cell. During cell degeneration following pollination the cytoplasmic clusters show Ca²⁺-CTC fluorescence. The used P. hybrida cultivar is self-fertile. The selection of pollen tubes occurs mainly in the upper part of the style. The rejected pollen tubes show a steady high level of membrane-associated calcium.