Staminodial Nectary Structure in Two Pulsatilla (L.) Species
In plants belonging to the Ranunculaceae the floral nectaries may differ in origin, location in the flower, shape and structure. In many cases they are defined as modified tepals or modified stamens. The nectary organs in this family are frequently termed "honey leaves," and staminodial origin is attributed to them. Gynopleural and receptacular nectaries are rarely found in Ranunculaceae. To date there are no reports on the structure of the nectary organs in plants of the genus Pulsatilla. We used light and scanning electron microscopy to study the location and structure of the nectaries in Pulsatilla slavica and P. vulgaris flowers. The staminodial nectaries were found to be nectar-secreting organs. The number of stamens per flower (102-398) increases with plant age. The share of staminodes is 12-15%. The staminodes are composed of a filament and a modified head. They are green due to the presence of chloroplasts in the epidermal and parenchymal cells. The parenchymal cells are in a loose arrangement. Stomata (3-20), through which nectar exudation occurred, were found only in the abaxial epidermis of the staminode head. The stomata are evenly distributed and have well-developed outer cuticular ledges. Some of them are immature during nectar secretion, with their pores covered by a layer of cuticle. During the activity of the nectariferous organs in the flowers, primary (on the staminode surface) and secondary nectar (at the base of tepals) are presented. The staminodes of the two Pulsatilla species show similar structural features and have similar shares in the androecium.