Nucleic Acid Metabolism during Germination of Pima Cotton (Gossypium barbadense)

The nucleic acid metabolism in long staple Pima cotton (Gossypium barbadense L.) was examined during the first 48 hours of germination at 34 C. Specific activity analysis of pulselabeled nucleic acids indicated that the first significant incorporation of precursors into DNA occurs at approximately 18 hours when the radicles are emerging with a peak of incorporation occurring at 36 hours. Specific activity of total RNA also indicate peak values at 18 hours and 36 hours of germination. Sucrose gradient analysis of pulse-labeled RNA indicated that the synthesis of ribosomal RNA reached a maximum value during the 18-hour period and that there was a shift in transcriptional products during the 30- to 36-hour interval. The extraction of the RNA from pulse-chase studies and from labeled polyribosomes suggest that a significant portion of the RNA synthesized at 36 hours appears to be messenger RNA and at 18 hours is ribosomal RNA. These distinct patterns of metabolism during germination provide a background for studying nucleic acid metabolism during chilling damage.