CYTOPHOTOMETRY OF NUCLEAR-DNA IN BUDS AND FLOWERS OF NICOTIANA-TABACUM

Feulgen/DNA absorptions were measured by scanning cytophotometry on the nuclei of meristematic cells in buds and flowers of Nicotiana tabacum developing in vivo or regenerating in vitro from thin cell layers excised from different plant parts and characterized by significant changes in the amount and organization of nuclear DNA. The results obtained indicated that, in vivo, nuclear DNA contents were significantly higher in flowers than in buds. Significant differences in the amount of nuclear DNA were also observed when comparing buds developing in vivo and in vitro and, among the latter, those regenerated from explants taken from different plant parts. Flowers developed in vivo and those regenerated in vitro, independent of which explants they were formed from, always have the same DNA content. These findings seem to suggest that rapid quantitative changes in the nuclear DNA having a possible role in developmental regulation can occur in Nicotiana tabacum.