Effects of trivalent and hexavalent chromium on root growth and cell division of Allium cepa

The effects of trivalent and hexavalent chromium on root growth, cell division and chromosome morphology of Allium cepa were studied. The concentrations used of chromium nitrate and potassium dichromate were 2 × 10-1, 2 × 10-2, 2 × 10-3, 2 × 10-4, 2 × 10-5, 2 × 10-6, and 2 × 10-7M. The results showed that both trivalent and hexavalent chromium inhibit root growth and cause mitotic irregularities comprising c-mitosis, anaphase bridges, chromosome stickiness, and chromosome fragmentation and lagging. When compared with chromium nitrate on the equimolar basis, potassium dichromate showed a stronger inhibitory and toxic effect on root growth and cell division, respectively. The possible mechanism of the Cr poisoning of root meristem cells of Allium cepa is also briefly discussed.