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The stigmatic papillae of sweet cherry were examined to determine developmental characteristics of the wet‐stigma surface. Early stages of secretion are detectable 1 wk prior to anthesis by using a 1% crystal violet solution. The number of stainable cells and the amount of interstitial staining subsequently increase, although secretions are not visible on unstained specimens until anthesis. Auto‐fluorescence above 500 nm (excited by 335–480 nm) becomes microscopically detectable at floral maturity and grows more intense after anther dehiscence. Light microscopy of plastic sections shows that papillae degenerate in peripheral regions of unpollinated mature stigmas, and that this is even more pronounced in pollinated ones. The distal portions of the papillae are covered with a homogeneous cuticular cap, which when viewed with electron microscopy encloses a subcutaneous secretion prior to cuticle exfoliation. Other exudates observed with electron microscopy prior to anthesis are interstitial electron‐translucent globules and surrounding matrix, and assorted vesicles, lipid globules, and starch grains which are present at floral maturity. Flowers observed under field conditions in the terminal secretion stage accumulate trichomatous structures. Our observations indicate that the stigma of Prunus avium L. is characterized by several phases of secretion which appear to be facilitated by mechanical abrasion. A model for the primary pollen‐receptive area is proposed and suggestions are made concerning the origin of the secretions.

The pollen tube of Prunus avium (cherry) consists of a growth zone of vesicles at the tip and an assemblage of organelles typical of an actively metabolizing cell. Electron opaque globules are closely associated with the plasma membrane and fibrillar cell wall layer at the tip. Acid phosphatase (EC 3.1.3.2) activity is localized in the membranes of 120 nm vesicles and ER system, the lumen of 50 nm vesicles, the plasma membrane and the tube nucleus.

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Proportions of cellular components in the midstylar transmitting tissue of Prunus avium L., sweet cherry, were determined using the point interception method on transmission electron micrographs. Changes were measured during the development of the style when comparing pistils collected 1 week before anthesis with unpollinated pistils at the anthesis stage. Transmitting tissue was also examined 20 h after cross- and self-pollination. The results illustrate complex patterns of cellular development including changes in vacuolation, cell wall – intercellular substances, and starch. Other cellular components were also quantified and are discussed. After pollination, further cell wall – intercellular substances increases occur but no differences were found between cross- and self-pollination.