ULTRASTRUCTURAL IMMUNOLOCALIZATION OF PERIODIC PECTIN DEPOSITIONS IN THE CELL-WALL OF NICOTIANA-TABACUM POLLEN TUBES

The monoclonal antibody (MAb) JIM5, marking acidic pectins, was used to localize ultrastructurally pectin molecules in the pollen tube wall of Nicotiana tabacum. Longitudinal sections of LR White embedded pollen tubes were exposed to antibody treatment; accumulations of pectins were identified by counting the density of the gold particles representing the pectin epitopes along the pollen tube wall. Significant accumulations of gold grains were marked and the distances between them were measured. In many pollen tubes a more or less regular distribution of the accumulations was observed along the tube indicating a periodical deposition of pectin. The distances between the accumulations were 4-6 mu m. Most of the label was found in the inner part of the outer layer of the bilayered cell wall. These findings correspond to and confirm the earlier observation by our group reporting ring-shaped periodical deposits in pollen tubes after immunofluorescence labelling with the MAb nM5 under the confocal laser scanning microscope.