Immunochemical and cytochemical detection of wall components of germinated pollen of gymnosperms

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Abstract
To elucidate wall construction of gymnosperm pollen, we studied the distributions of cell wall constituents in the germinated pollen of 14 species of gymnosperms in 8 genera and 6 families cytochemically with 4 staining dyes for polysaccharides, and immunochemically with 4 monoclonal antibodies for polysaccharides and 2 monoclonal antibodies for arabinogalactan proteins (AGPs). All intines and tube walls of the pollen examined contained AGPs and cellulose. Although having small differences, pollen of the Podocarpaceae, Pinaceae, Taxodiaceae, and Cupressaceae (Coniferales) had a similar composition of wall constituents: much AGPs occurred in both the intine and the tube wall, pectins were rare in the tube wall. On the other hand, in Cycas revoluta pollen, pectins were abundant and in Ginkgo biloba , g -(1,3)(1,4)-glucan was abundant in both the intine and the tube wall. The occurrence of g -1, 3-glucan in the intines was common to six Pinus species, but its occurrence in the tube wall differed among them. None of the gymnosperm pollen tubes examined had tube walls similar to those of angiosperm pollen, which consist of two layers, a pectic outer layer and a callosic inner layer. These results suggest that wall formation in gymnosperm pollen tubes is remarkably different from that of angiosperm pollen tubes and the composition of the wall constitutes may reflect a taxonomic relationship among gymnosperms.