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We investigated the influence of different concentrations of alcoholic extract from young shoots of Taxus baccata var. 'Elegantissima' (TbE), containing paclitaxel (81.6 µg/g fresh mass), on mitotic activity and DNA content in meristematic ` cells of Allium cepn adventitious root tips. During 24 hours of incubation we obtained different level of inhibition of mitotic activity: ranging from slight changes (dilution 1:32), through complete inhibition reversible in postincubation (dilution 1:8), to whole inhibition irreversible in postincubation (dilution 1:4). Inhibition of mitotic activity was connected with an increase of prophases and metaphases and changes in morphology of chromosomes (thick chromosomes of prophases with diluted karyolymph 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 method. The optimal concentration of the TbE extract, which inhibited mitotic activity, did not damage the genetic material (chromosomes) visibly

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We investigated the influence of extract from Taxus baccata var. Elegantissima (TbE) shoots in 1:8 dilution, containing paclitaxel in concentration of 81,6 µg/g fresh mass on ultrastructure and tubulin cytoskeleton of meristematic cells of Allium cepa L. root tips. Incubation time 3, 6, 12 and 24 h was followed with postincubation in water for 12 and 24 h. During shorter incubation (till 12 h) the surface of the cell nuclei decreased and chromatin became condensed (in comparison to control) but after 24 h the average surface increased and chromatin condensation decreased. In the course of incubation the average size of plastids and vacuoles increased. Moreover, after treatment mitochondria and plastids showed degradation of ultrastructure, which was reversed after 12 h of postincubation. Immunocytochemical assays demonstrated that in the course of incubation in the ThE extract, the tubulin cytoskeleton became partially disorganised. In most interphase cells, cortical microtubules (MTs) lost their oval transverse orientation. The preprophase band (PPB) position in the cell was often asymmetrical. The MTs array of the karyokinetic spindle and phragmoplast was also disturbed. These alterations were completely reversed during postincubation