Carbofuran induced cytogenetic effects in root meristem cells of Allium cepa and Allium sativum: A spectroscopic approach for chromosome damage

Cytogenetic effects of carbofuran were evaluated through chromosomal aberration assay on the root meristem cells of Allium sativum and Allium cepa to demonstrate relative sensitivity of both the plant systems with the test chemical. Ultraviolet and Fourier transform infrared (UV/FTIR) spectral measurements and molecular orbital calculations were also carried out to demonstrate the interaction of carbofuran with DNA. In primary toxicity assay, EC50 values of carbofuran for A. sativum and A. cepa root growth were determined to be 39.17 and 81.65 ppm, respectively, and test concentrations were selected by the EC50 value for A. sativum. For the cytogenetic assay, root meristem cells were exposed to 20, 40 and 80 ppm of carbofuran for 24 h and also left in water for 24 h recovery. Exposure of carbofuran showed significant and concentration-dependent inhibition of mitotic index and induction of mitotic and chromosomal aberrations (MA and CA). The frequency of MA and CA were relatively higher in A. sativum than A. cepa. The cell examined at 24 h recovery period minimized the effect of carbofuran on MI and percent aberrations; however, cells exposed to 40 and 80 ppm showed significant frequency of aberration despite substantial recovery. This study indicates the better sensitivity of A. sativum over A. cepa and may be used as a sensitive and efficient test system for the biomonitoring of environmental chemicals. A spectral shift observed in UV absorption study reveals that carbofuran binds with DNA. Importance of molecular vibrations involving atoms of the active site in the recognition (via polarization) and binding of carbofuran to DNA was discussed. Based on data on valence charge distributions, spectroscopic observations and structural features, a possible mechanism was proposed for the interaction of carbofuran with DNA resulting in chromosomal aberrations.