Characteristics of the generative sphere of <i>Danae racemosa</i> (Asparagaceae) under introduction in the Crimea peninsula

The article presents the analysis of the genesis of the flower reproductive structures of Danae racemosa (L.) Moench (Asparagaceae) – an evergreen shrub introduced to the Southern coast of Crimea. The natural range of the species covers Turkey, Syria, Transcaucasia and Iran. The inflorescences of D. racemosa contain flowers of three types: staminate, bisexual and pistillate. Cytoembryological analysis of the development of reproductive structures of D. racemose has shown that the main features of the male generative sphere of D. racemosa are the centripetal type of microsporangium wall formation; secretory tapetum; a successive type of microsporogenesis, microspore tetrads are isobilateral or tetrahedral. The wall of the mature anther has a layer of flattened epidermal cells and endothecium with fibrous thickenings. Pollen grains in D. racemosa are tricellular. The female generative sphere of D. racemosa is represented by anatropic, bitegmic, medionucellate ovules. Megasporogenesis takes place with the formation of a linear tetrad of megaspores. The embryo sac develops by Polygonum-type. In all D. racemosa flowers, regardless of the type, the rudiments of anthers and ovules are formed in the early stages. Fully functional male and female generative structures (anthers and ovules) develop in bisexual flowers. Morphologically normal pollen grains (about 70%) predominate in the pollen of such flowers. In staminate flowers, the female generative sphere undergoes reduction. Ovules degenerate at megasporocyte stage. In the pistillate flowers, anthers abortion occurs at microsporocyte stage, however, the anthers remain, and in some cases, a small amount of pollen is formed in them.