AN AUTORADIOGRAPHIC STUDY OF RNA SYNTHESIS DURING POLLEN EMBRYOGENESIS IN HYOSCYAMUS NIGER (HENBANE)

Abstract

RNA synthesis during pollen embryogenesis in cultured anther segments of Hyoscyamus niger (henbane) has been followed by autoradiography of 3H‐uridine incorporation. Embryogenic divisions were initiated in binucleate pollen grains in which the generative nucleus or both generative and vegetative nuclei synthesized RNA. When the first haploid mitosis in culture resulted in pollen grains with two nearly identical nuclei, those in which both nuclei synthesized RNA became embryogenic. Binucleate pollen grains in which 3H‐uridine incorporation was confined exclusively to the vegetative nucleus gradually became starch‐filled and nonembryogenic. Based on the degree of involvement of the vegetative nucleus in embryoid formation, some differences were noted between the counts of autoradiographic silver grains over cells cut off by the generative and vegetative nuclei during progressive embryogenesis. The possible significance of RNA synthesis in the nuclei of binucleate pollen grains in determining the pathway of embryogenic divisions is discussed.