ULTRASTRUCTURE OF ANOMALOUS POLLEN DEVELOPMENT IN EMBRYOGENIC ANTHER CULTURES OF HYOSCYAMUS NIGER

The formation of anomalous, binucleate pollen grains and their subsequent embryogenic development, induced by anther culture in Hyoscyamus niger, were analyzed by transmission electron microscopy (TEM). In culture, uninucleate pollen grains occasionally divided symmetrically giving rise to two apparently identical nuclei sharing a common cytoplasm. These nuclei divided once or twice unaccompanied by cell wall formation. After the daughter nuclei organized into cells, their subsequent division products contributed to embryoid formation. In conjunction with previous studies of pollen embryogenesis in H. niger, it appears that in contrast to the principle mode of embryogenesis (i.e., first asymmetric division forms typical two-celled pollen grain and the generative cell acts as the embryogenic precursor), anomalous pollen show no carry-over of gametophytic influences following embryogenic induction. This suggests that specific pathways of embryogenesis are correlated with the rate at which gametophytic gene activity is repressed following induction.