DNA SYNTHESIS IN PRIMARY ROOT OF GLYCINE MAX DURING GERMINATION

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Abstract
The percentage number of cells in S (cells which are undergoing DNA synthesis at time of treatment) in 4-mm root tips during early stages of germination was determined by tritiated thymidine and liquid emulsion autoradiography. Labeled nuclei were observed within all anatomical regions of the primary root 24 hours after seeds were sown and the observed labeling did not follow the known pattern of mitotic reactivation. This would indicate that DNA synthesis was not closely-related to the onset of mitosis during germination. The percentage of cells labeled was 10% at 24 hours, approximately 3% at 32 through 48 hours, and 10% at 60 through 96 hours after seeds were sown. The 3% labeled cells at 32–48 hours after planting may indicate a large population of G2 cells but this was not in accordance with a previous study on Glycine max, in which DNA per cell was determined. A greatly reduced labeling over the stelar and common initial regions indicates the existence of a quiescent zone in the embryonic root.