Th e study gives insight into the eff ects of manganese and lead microelements treatment on germination of Allium cepa L. Th e cytogenetic eff ects were studied by the calculation of the mitotic index, by the study of the interphase and chromosomal aberrations on the mitotic cells. We used MnSO 4 and Pb(NO 3) 2 solutions with diff erent concentrations: 0.0003, 0.003, and 0.03%. Th e Allium bulbs were preliminary imbued in water, and then they were treated for 12, 24 and respectively 72 hours in

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... these solutions. Th e control group was treated with water. We prepared fi ve cytological slides, for each slide we have studied 10 microscopic fi elds with good density of cells for the mitotic index and another 10 diff erent microscopic fi elds for abnormal interphases and chromosomal aberrations. In the analyzed meristematic cells we observed an almost totally inhibition of cell division and the mitotic index was smaller in comparison with the control variant. Th e study of the frequency of the cells in diff erent phases of the mitotic division showed that the highest percent was registered by prophases, followed at distance by telophases. Th e radicles formed in MnSO 4 solutions were characterized by the presence of disorganized nuclei, with an unusual structure of the chromatin fi ber and metaphases with expulsed chromosomes. In Pb(NO 3) 2 solutions there are observed anaphases with small bridge and telophases with small bridge and one micronucleus. We can conclude that the heavy metals Mn and Pb have a signifi cant mutagenic activity in vivo upon the radicles of A. cepa.