The Anatomy, Histochemistry and Ultrastructure of Stigmas and Styles in Commelinaceae

The anatomy and ultrastructure of stigmas in 37 species of 13genera of Commelinaceae are described. The stigmas are papillate,papillae forming a dense fringe of cells around the mouth ofthe stylar canal in most species. The papillar cell wall iscovered by an unstructured cuticle of variable thickness andis of variable thickness because of small wall ingrowths. Thecuticle and the external surface of the papillar cell wall arevariably disrupted, particularly in the mid and basal regionsof the cell. This was not found in species of the genus Aploleiaor Callisia. The cell cytoplasm possesses all major organellesexcept chloroplasts and each cell is vacuolate. In all species except Aploleia mulitiflora the style comprisesan epidermis, a cortex and a hollow, tripartite canal whichis continuous into the ovary cavity. The three vascular strandsare positioned at the apex of each canal lobe. The canal cellsare elongate and tabular and the wall abutting the canal hasingrowths. The style in Aploleia is solid and the transmittingtissue comprises cells whose walls are electron opaque. Thecytoplasms of both types of cell are similar in content althoughthere is a single, large vacuole in canal cells and many smallvacuoles in transmitting tissue. The morphology, position and histochemistry of stigmatic andstylar exudate was similar in all ‘wet’ stigmas.Most of the exudate originates from the stylar canal althoughsignificant contributions are made by the papillae in stigmasof Coleotrype, Dichorisandra and Thyrsanthemum. There is no apparent relationship between stigma structure andthe presence of self-incompatibility. Stigma papillae, stylar canal, transmitting tissue, Commelinaceae