Peculiarities of the reproductive biology of three species of genus Colchicum from Bulgaria

This study establishes the peculiarities of the major parameters of reproductive biology (features of the structures and processes in the male and female generative sphere, pollen and seed viability) of three species of genus Colchicum from the Bulgarian flora - Colchicum autumnale, Colchicum diampolis and Colchicum bivonae. The anthers are tetrasporangiate. Their wall develops according to monocotyledonous type and consists of epidermis, fibrous endothecium, two middle layers and glandular tapetum. The sporogenous tissue in the anther locule is one-layered. The microspore tetrads formed after regular meiosis in microspore mother cells and successive microsporogenesis are predominantly tetrahedral. The mature pollen grains are two-celled. The ovule is anatropous, medionucellate and bitegmic. In it a unicellular archesporium forms without cutting off parietal cells. The embryo sac develops after Polygonum (monosporic)-type. The embryogenesis follows the Asterad-type. The formation of an additional embryo derived from one of the synergids was found in C. diampolis. The endospermogenesis passes a free nuclear stage before its transformation in cellular one. The established high pollen and seed viability provides the investigated Colchicum species with high reproductive capacity.