ON THE REPRODUCTIVE BIOLOGY OF ALKANNA TINCTORIA (BORAGINACEAE)

In the present study main parameters of reproductive biology as features of embryological structures and processes as well as the pollen and seed viability of Alkanna tinctoria, an endangered useful species of Bulgarian flora were established. In its studied Bulgarian populations pollen viability above 90% and seed viability - between 32% and 64% were determined. The anthers are tetrasporangiate and their wall develops according to Dicotyledonous-type, consisting of an epidermis, fibrous endothecium, an ephemeral middle layer and secretory tapetum. The microsporogenesis is simultaneous and in the anthers tetrahedral and isobilateral microspore tetrads are formed. The mature pollen is three-celled at shedding stage. The ovule is anatropous, teniunucellate, unitegmic. Embryo sac (ES) develops according to the Polygonum (monosporic)-type. The embryo development follows the Asterad-type. The endosperm in the mature seeds has been completely consumed. As a result of the present study A. tinctoria is characterized as a sexually reproducing species.