Studies on the reversal of lead induced mitostatic effect in Allium Cepa root tip cells with myrobalan (fruit of Terminalia Chebula, Retz, Combretaceae)

The present study was undertaken to find the protective role of myrobalan against lead (Pb) induced cytogenetic effects on mitosis in Allium-cepa root tip cells. Onions were initially cultivated in deionized water for 3 days and were then exposed at 100, 1000, 3000 and 10,000 ppm of lead nitrate solution for 1 hr. After exposure to lead, the onions were allowed to recover naturally or in myrobalan suspension (0.01 mg/ml) for 72 hrs. The root color, mean root length (MRL) and mitolic index (MI) were recorded and the metaphases and anaphases were scored for chromosomal aberrations. During the natural recovery (NR), roots did not grow following 1000, 3000 and 10,000 ppm Pb exposure but myrobalan treated drug recovery (DR) showed root growth following 1000 and 3000 ppm Pb exposure. The root growth was observed in both NR and DR, more in DR in 100 ppm Pb exposure. Among the control, root growth during these periods and MI did not change throughout the experimentation. Pb exposure at all concentrations, lowered MI. NR was ineffective in Pb treated root tip cells as these were seen in interphase with hypertrophied nucleoli showing mitostatic effect. DR could not revert the mitostatic effect in root tip cells exposed at 10,000 ppm Pb, however, drug could do so in 100, 1000 ppm and 3000 ppm Pb exposure. Both, NR and DR reverted mitostatic effect after 100 ppm Pb exposure and the effect was observed earlier in DR. No chromosomal aberrations could be seen at 1 hr, the cells failed to show typical metaphase arrangement. The effect appeared dose dependent. DR reverted mitostatic effect from 1 hr onwards and completed at 72 hrs in 1000 and 3000 ppm Pb exposure. At 100 ppm Pb exposure, mitostatic effect disappeared at 48 hr in NR while in DR, it reverted after 24 hr. Control root tip cells showed no mitostatic effect.