Histophotometric DNA measurements onUmbelliferae, Solanaceae andCompositae, before and after crown gall tumour induction

Abstract

Histophotometric measurements of the relative amount of DNA per nucleus in control cells (meristematic cells of the plumula) and in differentiated cells (procambium and parenchyma cells of the first or second internode or leaf mesophyll cells) reveal that the investigated species, belonging to theUmbelliferae, Solanaceae andCompositae, differentiate within the diploid conditions. After crown gall transformation, the nuclear DNA amount remains within the diploid limits. However, a limited number of cells, grouped or spread in the tumour goes through an endomitotic cell cycle and becomes octaploid or even 16-ploid. The conclusion seems justified that a strong relationship exists between the nuclear condition in the host plant and in the tumour tissues. The importance of “primary” (releated to the mitotic stimulus and dedifferentiation of existing cells at the onset of tumour growth) and “secondary” phenomena (resulting from the specific physiology in the tumours) is discussed.