Control of DNA synthesis in inhibited and activated Agrostemma githago seeds

The relationships between DNA synthesis and germination capacity of Agrostemma seeds had been studied. Protein synthesis and RNA synthesis were activated at the very beginning of imbibition, whereas DNA synthesis started in the second part of the imbibition phase. Agrostemma seeds inhibited by higher temperature (30 degC), or aged seeds with a low germination capacity were characterized by a significantly reduced protein synthesis. DNA synthesis was also reduced. The inhibition of the protein synthesis of Agrostemma embryos fed with cycloheximide or actinomycin D caused a depression of DNA synthesis. The results indicated that the initiation of DNA synthesis of imbibing Agrostemma seeds depended on the synthesis of special proteins. Abscisic acid inhibited the growth as well as DNA synthesis of isolated Agrostemma embryos. Nitomycin inhibited germination and DNA synthesis to the same extent. Dormant seeds with an undiminished intensity of protein synthesis also showed a reduced incorporation of 3H-thymidine by DNA. It is suggested that DNA synthesis of imbibed seeds, which is a necessary prerequisite for the radicle protrusion, was involved in the mechanism of ripening of the Agrostemma seeds. (author)