Chromatin-bound DNA-dependent RNA polymerase in developing pea cotyledons.

The pattern of cotyledon development in three varieties of Pisum sativum has been defined in terms of cell number, DNA and RNA content and chromatin, bound RNA polymerase activity. Variation was observed in the relative periods of growth by cell division and cell expansion between the three varieties. The mean DNA content per cotyledon cell during growth by cell expansion increased to approximately 50C in one variety, 30C in the second variety and 15C in the third variety. The pattern of chromatin-bound RNA polymerase activity during development suggested that some of the DNA above the 2C level may contribute to RNA synthesis in two of the three varieties studied. In the third variety the RNA polymerase activity decreases throughout the phase of increase in DNA per cell. The chromatin-bound RNA polymerase activity per cell was correlated with the rate of RNA increase per cell.