Toxicity of some heavy metals in vivo and in vitro in Helianthus annuus.

To compare the toxicity of some heavy metals in vivo and in vitro, the effects of six metals, aluminum (Al), cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) were studied in the oil-yielding plant Helianthus annuus. The percentage of seed germination and cytotoxic effects at different concentrations and durations of treatment as well as the growth rate of callus tissues in vitro were compared to ascertain the concentrations that can either support plant growth or cause lethality. Highest toxicity to the plant system was observed from the effects of Pb both at high and low concentrations whereas Zn was the least toxic; and similar effects were seen in vivo and in vitro. The clastogenic effects of Al, Cd, Cu, and Ni were dependent on concentration and length of treatment. Cu and Zn showed less severe cytotoxic damages than Al, Cd, Pb, and Ni. In vitro growth could be supported at 100-1000 times the diluted concentrations of the metals in comparison to in vivo treatment.