Description:
<jats:title>Abstract</jats:title>
<jats:p> An in vitro transcription system using nuclei from freely suspended callus cells of Petroselinum crispum is described. The use of a filtration technique allowed the measurement of transcription and release of RNA simultaneously over very short time intervals. The transcription showed a biphasic time course, with an early maximum at 2 and a later one at 20 minutes. The early maximum was ascribed to the activity of polymerase II (α-amanitin sensitive), the later to that of polymerase I. While the transcriptional process was independent of the temperature used for incubation up to 26 °C and even increased with temperatures above that, the release of RNA transcribed was inhibited by temperatures above 36 °C.</jats:p>