RNA synthesis during pollen germination.

Regulation of pollen germination of Petunia was investigated by determining RNA content and composition in an in vitro system in the presence and absence of the transcription inhibitor actinomycin D and by labelling with C14-orotic acid.At the beginning of the progamic phase 2 stages can be distinguished: First (up to 15 minutes) no essential RNA synthesis occurs, but merely a release takes place of the protein-bound RNA carried by the pollen grains. The second stage (up to 60 minutes) shows only little RNA synthesis which has not the main regulatory function.At the RNA translation level germination is controlled mainly by activation and inactivation of long living RNA.