Immunocytochemical localization of esterified and unesterified pectins in unpollinated and pollinated styles of Petunia hybrida Hort.

Localization of pectins in the style of Petunia hybrida before and after po llination was investigated by immunocytochemistry using two primary monoclo nal antibodies specific to highly (JIM7) and weakly (JIM5) methylesterified pectins. In the unpollinated style, esterified pectins occur-red mainly in the cell walls of cortex tissue, while unesterified pectins were present m ainly in the extracellular matrix (ECM) of the transmitting tract. After po llination no remarkable differences were found in pectin distribution in th e ground tissue of the style. On the other hand, in the transmitting tract a reduction in the quantity of unesterified pectins was observed. Unesterif ied pectins in the extracellular regions of the transmitting tissue decreas ed before the penetration of the pollen tubes, indicating that pollination induces a reduction in the amount of unesterified pectins in the transmitti ng-tract ECM. The correlation between the degradation of strongly Ca2+-bind ing pectins and the growing level of those ions in the extracellular region s of the transmitting tract in the pollinated pistil of P. hybrida (M. Lena rtowska et al. 1997) suggests that this process may constitute a mechanism for creating an optimum calcium medium for in vivo-growing pollen tubes. Bo th pectin categories were localized in pollen tubes. Esterified pectin epit opes were localized mainly in the vesicles of the tip cytoplasm. Unesterifi ed pectin epitopes were found in the external fibrillar wall of pollen tube s.