INTRASPECIFIC AND INTERSPECIFIC REPRODUCTIVE BARRIERS IN CROCUS (IRIDACEAE)

The reproductive system was studied in Crocus genus (Iridaceae) follow ing intra- and interspecific pollination, by using light and scanning electron microscopy. The results suggest that the stigma-style tract o f the Crocus pistil is a mere promoter of pollen tube growth, while in tra- and interspecific discrimination of compatible and incompatible p ollen occurs in the ovarian tract. Here, the transmitting tissue consi sts of special epidermal cells, whose granular or floccular secretions provide the selective medium for the growth of pollen tubes. The ovar ian self-incompatibility (SI) is widespread within the genus, resultin g in a partial or complete suppression of self-fertilization. Moreover , postzygotic SI mechanisms, as well as postzygotic mechanisms of unkn own nature, seem to be recurrent and both are responsible for seed abo rtion. The interspecific ovarian incompatibility concerns only unrelat ed crosses; crosses between related fertile species succeed both in fe rtilization and seed-set.