EFFECTS OF HEXAVALENT CHROMIUM (VI) ON ROOT GROWTH AND CELL DIVISION IN ROOT TIP

The effects of different concentrations of Cr(VI) (10-6 M to 10-3 M) on root growth and cell division in root tips of Amaranthus viridis L., were studied. Chromium (VI) had toxic effects on the root tip cells during mitosis, such as colchicine mitoses, anaphase bridges, chromosome stickiness. Chromosome stickiness implied the high toxicity of Cr(VI). The mitotic index decreased with increased concentration of Cr(VI), duration of treatment time and the ratio of anomalous dividing cells reversed. The results also indicated that the root growth was completely stopped by 10-3 M Cr(VI) after 24 h treatment time, and slightly inhibited by 10-4 M Cr(VI) during the whole experiment. Chromium (VI) had a stimulatory effect on the root growth of A. viridis L. exposed to 10-5 M Cr(VI) during the entire experiment. The mitotic index in the present study can be correlated with rate of root growth, suggesting that the inhibition of root growth resulted from inhibition of cell division