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

Abstract

The effects of trivalent and hexavalent chromium on root growth, cell division and chromosome morphology of ANium cepa were studied. The concentrations used of chromium nitrate and potassium dichromate were 2 x lo-', 2 x 2 x loW3, 2 x loW4, 2 x loW5, 2 x 10W6, and 2 x 10W7M. 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. Donghua Liu and Wusheng Materials and methodsHealthy and equal-sized bulbs were chosen from a population of the common onion Allium cepa L. (2n = 16). The onions had neither started shooting of green leaves nor started any growth of roots. Before starting the experiment, the outer dry scales of the bulbs were removed and the ring of the root primordia was left intact. 12 onions were the starting material in each series and the best 10 onions were selected on day 1 or day 2 for the continued test ( FISKESJ~ 1988).The concentrations used of chromium nitrate (Cr(NO,), . 9H20) and potassium dichromate (K,Cr,O,) were 2 x lo-', 2 x ]OW2, 2 x lo-,, 2 x 2 x 2 x lop6, and 2 x lO-'M. The solutions were prepared in tap water. Control roots were treated with tap water. The onions were placed directly in the test liquids, which were changed regularly every day. The bulbs were allowed to germinate producing roots in beakers at room temperature, 21"C, for 24, 48, 72, and 96 h. Macroscopic observations were made at the end of each time interval. The roots were cut and fixed in Carnoy's fixative (3 parts 95 % ethanokl part acetic acid, glacial) for 48 h, followed by squashing

Tolerance and prospection of phytoremediator woody species of Cd, Pb, Cu and Cr

“…Chromium toxicity affects the length of the primary roots and promotes changes in the architecture of the entire root system (Samantaray et al, 1996). The inhibitory effect of Cr on root growth (Barbosa et al, 2007) and its toxic effects on cell division result from the fixation of Cr 3+ by plant tissue and disturbances of the osmotic relations that promote restrictions to Ca 2+ transport through the plasma membrane to the cytoplasm (Liu et al, 1992).…”

Comparative genotoxicity of heavy metals in root meristems of <i>Cuminum cyminum</i> L.

“…The Active Mitotic Indices reflects the frequency of cell division and it is regarded as important parameter while determining the rate of root growth (Liu et al 1992). Genotoxicity of heavy metals is reflected by the gradual decrease in Active Mitotic Indices as concentration of doses increased (Fig.…”

Cytogenetic Effects of Crude Extracts of <i>Peganum harmala</i> Seeds and Their Effects on <i>Vicia faba</i> Plants

“…The presence of stickiness has been interpreted to be due to depolymerization of DNA (Abraham and Kashy 1979), DNA condensation (Osterberg et al 1984) or physical adhesion of chromosomal proteins (Patil and Bhat 1992). Liu et al (1992), El-Ghamery et al (2000) and Tipirdamaz et al (2003) reported that stickiness reflects a highly toxic and usually irreversible effect that probably leads to cell death.…”