Development of the Stigmatic Surface of Prunus Avium L., Sweet Cherry

Abstract

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.

Stigma Development and Receptivity in Almond (Prunus dulcis)

“…The cuticle-pellicle layer is torn away with continued secretion of exudates (Konar and Linskens, 1966;Dumas et al, 1978). In sweet cherry, the primary pollenreceptive area was associated with cuticle exfoliation and papillae degeneration (Uwate and Lin, 1981). Our observations concur in that an intact cuticle layer was only observed in early stage flowers, characterized as having minimal amounts of stigmatic secretion.…”

“…Papillae degeneration and the production of exudate have been associated with the beginning of stigma receptivity in tree crops such as sweet cherry and peach (Uwate and Lin, 1981;Herrero and Arbeloa, 1989). Rupture of cuticle layers during development of wet stigmas is associated with exudate production originating from epidermal and subjacent cell layers, that accumulates in the intercellular spaces of the stigmatic tissue and below the cuticle-pellicle layer of epidermal cells.…”

Asynchronous development of stigmatic receptivity in the pear (Pyrus communis; Rosaceae) flower

“…Stigma development and stigmatic receptivity-In this work stigma development has been characterized in the pear flower from anthesis to degeneration. Stigma structure, exudate production, and pollen tube penetration are similar, as has been described for other genera of the Rosaceae family such as Malus and Prunus (Heslop-Harrison, 1976;Uwate and Lin, 1981;Heslop-Harrison and Heslop-Harrison, 1982;Viti, Bartolini, and Minnocci, 2000). A layer of mainly papillate cells composes the receptive surface.…”

“…Stigma characterization has been widely illustrated both from an anatomical (Konar and Linskens, 1966a;Heslop-Harrison and Shivanna, 1977;Owens and Kimmins, 1981;Uwate and Lin, 1981;Ghosh and Shivanna, 1982) and biochemical (Konar and Linskens, 1966b;Martin, 1969;Labarca, Kroh, and Loewus, 1970) perspective. This has allowed an understanding of stigma morphology and exudate composition.…”

Characterization of Stigma Exudates in Aqueous Extracts from Apple and Pear Flowers

“…Given the importance of the stigma to fruit development in agriculturally prominent species in Rosaceae, there is surprisingly little information about the composition of stigma exudates of plants in this group. Although such data are extensive for a number of other flowering plants (Knox, 1984), studies involving rosaceous species are limited to histological investigations indicating the general presence of intercellular carbohydrates, proteins, and lipids in stigmatic tissue (Cresti et al, 1980;Stant, 1981;Uwate and Lin, 1981) and to the recent focus on S-RNases (Certal et al, 1999;Ishimizu et al, 1996;McClure and Franklin-Tong, 2006;Sonneveld et al, 2005). The deficiency of information for tree fruit species may be partly the result of the relatively small size of stigmas and brevity of the bloom period.…”