The initiation and maintenance of cell division in Jerusalem Artichoke tubor tissue has been investigated in 2 different ways: 1. A kinetic analysis of ribosomal RNA synthesis and maturation was undertaken to determine the points where accumulation of this RNA is regulated. The evidence presented indicates that the massive increase in the level of RNA in response to auxin is in part due to an enhancement in transcription of the precursor rRNA and in part due to pout-transcriptional control involving an increase in the rates and degree of processing of the precursor to the mature rRNA. 2. The acidic proteins of the nucleus and the cytoplasm were investigated during the early stages of culture, prior to the onset of coil division in the auxin treated tissue. Both the synthesis of these proteins and their modification by phosphorylation were monitored by the highly discriminating 2-dimensional gel electrophoresis technique. Significant changes in the acidic proteins of the nucleus were found early in culture, with approximately 6 additional proteins being synthesized and accumulated in this organelle. As 0-1 phase progressed, the number was increased to 20 and then to 40 at the start of DNA replication. Alterations in the phosphorylation pattern occurred only at S, with the specific modification of 6 proteins. No changes in the cytoplasmic proteins were detected.