The nature of secretion products forming the pellicle of the dry-type stigma surface has been investigated in Brassica by an electron-microscopic cytochemical study. In order to determine whether the pellicle is organized like a membrane, we used a series of cytochemical methods to visualize cell membranes. Three groups of techniques presenting different degrees of specificity in terms of cell surface markers have been used: non-specific labelling of cell-surface components, characterization of glycoconjugates and localization of enzymic activities. We demonstrated that the pellicle of Brassica stigmas, although not possessing a trilamellar structure, presents numerous characteristics encountered in biological membranes. In particular, it possesses cytochemically demonstrable enzyme activities, including ATPase and adenylate cyclase, whose role remains to be elucidated in relation to the pollen-stigma interactions.

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