Localization of pectins in the pollen tube wall of Ornithogalum virens L-does the pattern of pectin distribution depend on the growth rate of the pollen tube?

Monoclonal antibodies that recognize pectins were used for the localization of esterified (JIM7) and acidic, unesterified (JIM5) forms of pectin in po llen tube walls of Ornithogalum virens L. (x = n = 3). The results indicate d that the distribution of the two forms of pectin in the pollen tube wall depended on the medium (liquid or solid) used for pollen germination. In po llen tubes grown in the liquid medium, the localization of JIM7 was limited to the very tip of the pollen tube, whereas the localization of JIM5 indic ated a uniform distribution of unesterified pectins in the very tip of the tube and along the subapical parts of the tube wall. In tubes germinated on the medium stabilized with agar (1-2%) the localization of JIM7 and JIM5 i ndicated the presence of both forms of pectin in the tube tip and along the whole length of the pollen tube wall in a ring-like pattern. Thus, the loc alization of esterified pectins in the sub-apical part of the pollen tube w all, below the apex of the tube, is described for the first time. Measureme nts of the growth rates of pollen tubes growing on the two types of medium indicated that oscillations in tube growth rate occur but these do not coin cide with the pattern of pectin distribution in the tube wall. Our results complement the previous data obtained for the localization of JIM5 and JIM7 in pollen tube walls of other plant species. (Y.-Q. Li et ar. 1994, Sex Pl ant Reprod 7: 145-150) and provide new insight into an understanding of the construction of the pollen tube wall and the physiology of pollen grain ge rmination.