INHIBITION OF RNA AND DNA SYNTHESIS IN VICIA ROOTS BY 8-ETHOXYCAFFEINE (EOC).

The effect of EOC, one of radiomimetic chemical.;, on the incorporation of 32Pi into RNA and DNA was investigated with the primary roots of Vicia seedPng. The presence of EOC during the period of labelling with 32Pi did inhibit partially or almost completely, depending on the concentrations of EOC, the incorporation of the isotopes into RNA and DNA. The extent of the inhibitory effect by EOC was approximately identical among the fractions of rRNA, mRNA, and the low molecular-weight RNA fraction consisting of tRNA and 5-6S RNA, thus indicating that the action of EOC on chromatin is not of preferential nature to the nucleolar organizer region, though EOC is known to induce the chromosome breaks which are extremely localized to the secondary constriction.