Feulgen-DNA Content and Acid Lability of Nuclei fromin Vivoandin VitroNormal, Wound and Crown Gall Tissue ofNicotiana TabacumL.

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Abstract
We studied the changes in DNA brought about in nuclei from in vivo and in vitro normal, wound and crown gall tissues of Nicotiana tabacum L., by measuring the Feulgen-DNA content of 8850 nuclei with a scanning and integrating microdensitometer. We obtained the following results. 1) In vivo tissues: nuclei of young tumour cells are more susceptible to hydrolysis (1 N HCl, 60°C) than nuclei of normal, wound and aged tumour cells, 2) In vitro tissues: the hydrolysis curves of callus and tumour nuclei run parallel; there are no significant differences between young and mature tissues; nuclei from tumour cells always stain significantly less than those from callus cells. Aneuploidy or differences in the degree of chromatin condensation are a less likely explanation for this phenomenon. It may be correlated with the state of DNA replication (less protection by histones). We found no evidence either for a correlation between tumoural transformation and DNA content or chromosome number, or that tumour tissues would have a greater tendency for polyploidy than callus cells.