Genotoxic Effects of Cobalt Chloride on Mitotic Index of Allium cepa L

Root meristem cells are highly sensitive to genetic damage by chemicals; hence, present work is undertaken to assess the effect of different concentrations of Cobalt chloride on mitotic index of Allium cepa L. Experiments were conducted by using onion bulbs. These bulbs are planted in paper cups containing sand and soil mixture (2:1 ratio) and plants were treated with different molarity (M) of Cobalt chloride. The roots were macerated to analyze the mitotic index and chromosomal abnormalities. The mitotic index was 11.55%, 11.33% and 10.988% for the treatment with 0.5, 1.0, and 1.5M CoCl2 respectively and it was least (9.1%) with 2.5M of CoCl2. Maximum interphase cells (409) were observed with 2.5M, compared with the control and other treatments (0.5M: 398 cells, 1.0M: 399 cells and 1.5M 401 cells). The plants treated with 1.5M and 2.0M CoCl2 have the highest number of metaphase cells (16) and less number of cells with anaphase observed in plant roots treated 2.5M CoCl2 (2 cells) followed by 0.5M and 2.0M CoCl2. The total chromosomal abnormalities in the root tips treated with 2.5M CoCl2 are 21(51.2%) was observed. Micronucleus of budding nucleus have an approximate half percentage 9 (21.9) whereas C-mitosis and chromosome stainless have the same proportion 3(7.3). It was noted that, the unequal sized 5 nuclei (12.1%), the anaphase bridge has the lowest percentage 1(2.04%) on the other hand 2.5M CoCl2 conc., has only 1(1.91) of C-mitosis and chromosome stainless. The study highlights that, the higher concentration of heavy metals have negative effect on the mitotic index of root meristematic cells.