Cytomorphologic parameters in monitoring cytogenotoxic effects of fertilizer in Allium cepa L.

The present investigation was done to assess cytomorphologic parameters as indicators of genotoxicity as it is a simpler method and could be suggested for rapid screening of the vast range of agrochemicals used all over the world. The excessive and indiscriminate use of agrochemicals is responsible for increasing the level of pollutants in the soil environment resulting in cellular and molecular damage to the plants. The cellular damage caused manifestation of the resulting oxidative stress due to pollutants which can go up to the level of DNA. The roots of Allium cepa were treated with 0.5 mg N ml-1 concentration of ammonium nitrate fertilizer for 3, 6, 9 and 12 h, and in mitotic preparation of their respective root, mitotic index, phase indices and the genotoxic markers viz. chromosomal aberrations and binucleate cells were observed and the data statistically analysed. A significant decrease in mitotic index and increase in abnormality percentage as compared to control was observed which increased with the treatment duration. Chromosomal aberrations like stickiness, fragmentation, precocious movement, bridges and disorientations were observed in varying frequencies. A cytomorphologic study revealed that the interphase cell volume of cells of treated roots and their respective interphase nuclear volume were reduced as compared to control. The ratio between nuclear and cytoplasmic volume has been reported to relate to cell integrity. Both these markers viz. cytomorphologic and genotoxic can be used for assessment of the toxicity of agrochemicals including fertilizer; in our study, they have revealed the cytogenotoxic behaviour of ammonium nitrate fertilizer.