GENOTOXIC EFFECTS OF SODIUM NITRATE IN ONION ROOTS

The scope of this paper is to assess cyto- and genotoxic effects of sodium nitrate on Allium cepa root tips by using different concentrations (i.e. 0,1%; 1% and 5%) for treating uniform healthy onion bulbs for three different periods of time: 6, 24 and 72 hours. In the end of the experiment the harvested root tips were prepared according to Feulgen's squash technique using Schiff reagent and the investigations were realized according to Allium test. The cytotoxic and genotoxic effects of nitrate were investigated by calculating the mitotic index and observing all chromosomes' complement alterations during the mitosis. The phase rate of cells undergoing mitosis is also studied. For microscopy investigations a Novex Holland B microscope with digital camera included was used. The cytogenetic analysis of nitrate effects revealed a strong decrease in the mitotic index which is more intense with the concentration and time of exposure. Moreover, this effect is associated in case of the variant treated with 5% sodium nitrate acting for more than 24 hours, with the appearance of genotoxic effects such as chromosomal alterations, highly condensed chromatin expression easily identified during mitosis stages, sticky chromosomes and chromosomal bridges and laggards.