The experiment was conducted to study the inhibition of the root growth, cell division and cytotoxic effects of NaCl on onion bulbs (Allium cepa). The onion bulbs were treated with different concentrations of NaCl (0.06, 0.12, 0.24 and 0.48 molarity) for 72 hours in a glass beaker. The results, based on the different concentrations and exposure time showed that the mitotic index and the average onion root growth rate decreased significantly compared with the control. Treatment with 0.48

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... NaCl concentrations has a less percentage of root growth (12.9%) whereas treatment with distilled water (control) has maximum root growth (40.63%). The mitotic index of control was (12%) while onion treated with NaCl was decreased to (9.11%) in 0.48 molarity. It was found that the chromosomal aberrations increased as the concentration of the NaCl increased when compared to control. The recorded chromosomal abnormalities were micronuclei, budding nuclei, unequal-sized nuclei, c-mitosis, anaphase bridge, and chromosome stickiness. The results showed that the higher concentrations of NaCl have more impact on the root growth, cell division and chromosomal abnormalities of the root tips of the onions.