Influence of extract from shoots of Taxus baccata var. 'Elegantissima' on mitotic activity of meristematic cells of Allium cepa L. roots

We investigated the influence of different concentrations of alcoholic extr act from young shoots of Taxus baccata var. 'Elegantissima' (TbE), containi ng paclitaxel (81.6 mu mg/g fresh mass). on mitotic activity and DNA conten t in meristematic cells of Allium cepa adventitious root tips, During 24 ho urs of incubation we obtained different level of inhibition of mitotic acti vity: ranging from slight changes (dilution 1:32), through complete inhibit ion reversible in postintubation (dilution 1.8). to whole inhibition irreve rsible in postincubation (dilution 1:4). Inhibition of mitotic activity was connected with an increase of prophases and metaphases and changes in morp hology of chromosomes (thick chromosomes of prophases with diluted karyolym ph and c-metaphases). During the experiment. the number of aberrations and micronuclei didn't increase but the number of cells with replicated DNA (4C ) blocked in G2 phase was higher. This study was done by a flow cytometry m ethod. The optimal concentration of the TbE extract, which inhibited mitoti c activity, did not damage the genetic material (chromosomes) visibly.