Sequence of Reactivation of Ribonucleic Acid Synthesis during Early Germination of the Maize Embryo.

The onset of RNA synthesis in primary roots of germinating Zea mays embryos was studied. Incubation of excised embryos in the radioactive precursor solution was performed after different germination periods.It was observed that there are three successive stages in the reactivation of RNA synthesis. Stage one is characterized by the synthesis in the chromatin of heterodisperse nuclear RNA rich in adenine. Stage two is characterized by the synthesis of heterodisperse nuclear RNA in the chromatin and 2.3 x 10(6) rRNA precursor in the nucleolus. Stage three is characterized by the synthesis of heterodisperse nuclear RNA and rRNA precursor and by the processing of the latter in mature rRNA.