Monitoring of genotoxic risks of nitrogen fertilizers by Allium cepa L. mitosis bioassay

Abstract

The present study deals with the assessment of genotoxic effects of the two most commonly used nitrogen (N) fertilizers, ammonium nitrate and urea, using the Allium cepa L. root mitosis bioassay system. Allium cepa mitosis bioassay is known for its sensitivity and it is a classical test for studying chemical toxicity. A pot experiment was set up, in which ammonium nitrate and urea were added to soil at the rate of 200 mg N kg−1 soil. Roots from onion bulbs were fixed in the first and second week after treatment (WAT). Cytological analysis revealed dividing cells and different types of dividing cell anomalies and interphase nuclear anomalies. Per cent mitotic index and per cent anomalies in dividing cells were significantly higher in ammonium nitrate treated root tip cells. Urea proved to be mitodepressive in both weeks. Anomalies in dividing cells and interphase nuclear anomalies were also observed in the second WAT in both treatments. Per cent interphase nuclear anomalies were higher in case of urea. Therefore, nitrogen fertilizers should be used judiciously, to avoid or minimize the genotoxic risks.