RNA polymerases I and II in germinating wheat embryo.

1. The RNA polymerase I was practically absent in the resting embryos and appeared several hours after the beginning of imbibition, whereas the level of polymerase II was high in the resting embryos and did not increase significantly during the imbibition phase. 2. Incorporation in vivo of [14C]valine into polymerase I and II indicated that the synthesis of RNA polymerase I is initiated in germinating embryos much earlier than that of RNA polymerase II. 3. It is suggested that RNA polymerase II is stored in resting wheat embryos to support mRNA synthesis at the onset of germination, whereas the RNA polymerase I activity appears at a further stage of germination.