Effects of Cu2+ on root growth, cell division, and nucleolus of Helianthus annuus L.

The effects of different concentrations (10-5 - 10-2 M) of copper sulfate on root growth, cell division and nucleoli in root-tip cells of Helianthus annuus L. were investigated. Cu had an inhibitory effect on the root growth at 10-4 - 10-2 M during the entire treatment. Cu has toxic effects on chromosomal morphology including anaphase bridges and chromosome stickiness and on nucleoli, causing some similar silver-stained particulate material scattered in the nuclei. Once the nucleolus is poisoned, showing some silver-stained particles scattered in the nucleus, the root growth of H. annuus is obviously inhibited. And once more silver-stained particles appear in the nucleus, the root growth is almost or completely stopped. The possible mechanism of the Cu poisoning of root-tip cells of H. annuus is also briefly discussed.