Structure of the stigma and style in Colletia and Discaria (Rhamnaceae: Colletieae)

Abstract

The ultrastructure of the stigmas and styles of Colletia paradoxa, Colletia spinosissima, and Discaria americana was studied by transmission electron micros- copy before and during anthesis. The purpose of the study was to contribute a full description of possible interactions between the male gametophyte and the sporophytic tissues of the stigma and the style. Ultrastructure changes in the stigmatic papillae and epithelial and sub-epithelial cells of the stylar channels in relation to pollen tube growth are discussed and compared between species. New pollen tube pathways are described for hollow styles.