Initiation of DNA synthesis by kinetin and experimental factors in tobacco pith tissues in vitro

Since previous investigations had suggested that kinetin, like auxin, may initiate DNA synthesis in tobacco pith cells, a study was undertaken to learn whether the observed incorporation of tritiated thymidine into nuclear DNA in the presence of kinetin could be explained by different experimental factors.Pith tissues were isolated and allowed to rest a few days after excision and they were then placed on White's basic medium or on that medium supplemented with either one or both of the growth regulators in the presence of tritiated thymidine.The results of those studies, obtained by radioautographic and liquid scintillation counting methods, showed no statistically significant differences between pith tissues kept on the control medium and those on kinetin-containing medium. Similar tissues placed on an auxin or auxin- and kinetin-containing medium showed, as expected, a significant incorporation of tritiated thymidine into the DNA of pith cell nuclei.