Summary
Pith tissue was cultured on modified White’s nutrient medium supplemented, except for controls, with 2 mg/l of IAA and/or 0,5 mg/l of kinetin. For autoradiographs sections were used from tissue grown on medium containing tritiated thymidine.
Nuclear DNA contents (Feulgen) were measured by the microspectrophotometric two-wavelengths method. No fading of Feulgen dye in nuclei was found in 11 weeks, in contrast to considerable fading observed in earlier work when a different batch of basic fuchsin had been employed.
Counts of radioactive nuclei in autoradiographs agreed well with microspectrophotometric results on the occurrance of DNA synthesis.
In control cultures, with or without tritiated thymidine, DNA doubling took place in about 20% of the nuclei during the first two days but in few, if any, thereafter.
It was confirmed that kinetin, as well as IAA, increases the frequency of nuclei undergoing DNA synthesis. However, IAA, in contrast with kinetin, still induced considerable DNA doubling after two days. Continued cell reproduction was maintained only in the presence of both substances.
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This work has been supported in part by research grants toK. Patau from the US Public Health Service (grant No. C-3313) and the American Cancer Society; and by grants toF. Skoog from the American Cancer Society and the Research Committee of the University of Wisconsin Graduate School with funds from the Wisconsin Alumni Research Foundation.
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Das, N.K., Patau, K. & Skoog, F. Autoradiographic and microspectrophotometric studies of DNA synthesis in excised tobacco pith tissue. Chromosoma 9, 606–617 (1957). https://doi.org/10.1007/BF02568095
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DOI: https://doi.org/10.1007/BF02568095