Abstract:

The stigma initiation and development of Cucumis sativus L. female flower was studied using electron microscopy. The differentiation of stigmatic cells could be recognized when the floral bud was about 1 mm in length. After the pinnate structure of the stigma appeared, three regions indicating the papillae, the transmitting tissue and the secretory tissue were observed. The pinnate stigma was characterized as a partition structure for naming immature and mature stigma in the following investigation. The ultrastructure of various tissue cells of the stigma during the development was observed using transmission electron microscopy. Throughout the whole developmental process the cytoplasm of papillae and secretory tissue cells was filled with many endoplasmic reticula (ER). Most of the ER was tube-like and rough with enlarged cisterna from which many vesicles were produced. In the mature stigma, numbers of plasmodesmata were found between the secretory and the transmitting tissue cells. The papillae and secretory tissue cells are highly vacuolated and the plasmalemma was invaginated or exvaginated. The nuclear envelope of secretory tissue cells was enlarged, which led to the formation of plurivalvis nucleus during stigma development. Apparently, nuclear envelope became more strongly lamellate at mature stage. In different tissue cells of mature stigma, ATPase activity was localized along the plasmalemma and vacuole membrane. The PM-H⁺-ATPase specific activity increased during stigma development. Our results revealed the glandular characteristics of the developing stigma of cucumber female flowers.

Key words: Cucumis sativus(cucumber), stigma development, ultrastructure, ATPase