CONICET | Buscador de Institutos y Recursos Humanos

Prezygotic ovule abortion may lead to the partial or complete reduction of fertile ovules in the ovary and then is the primary factor that determines the sexual expression of the whole plant. In different plant species, ovule abortion was associated with the presence of callose in advanced ovules. Based on these observations we studied the pattern of ovule development and callose deposition in both hermaphrodite and female-sterile flowers of the andromonoecious shrub Caesalpinia gilliesii. The obtained results showed that all ovules complete the 8-nucleate stage of development and exhibited callose deposition at advanced stages. Nevertheless, from the 2-nucleate stage, a distinct spatial pattern of callose deposition within the ovule was observed between fertile and female-sterile flowers. Differences in callose deposition suggest that not callose per se but its distribution pattern in the ovule tissues is the main factor that triggers ovule isolation and abortion and leads to the female sterile condition of some flowers in this species. Furthermore, previous observed differential growth rates between hermaphrodite and male flowers support for resource depletion as the likely underlying mechanism of prezygotic ovule fate in C. gilliesii.