Effects of Metal Toxicity on Growth and Pigment Contents of Annual Halophyte (A. hortensis and A. rosea)

The toxicity of four potentially toxic trace elements (Cu, Ni, Pb and Zn) to Annual Atriplex (A. hortensis and A. rosea) was examined to determine if this plant showed sufficient tolerance to be used to phytoremediate soils polluted with these heavy metals. The soils, which contained up to (per kilogram) 501 mg Cu, 1674 mg Ni, 1334 mg Pb and 3588 mg of Zn were sampled around metal-contaminated site in southwest of France. We submit therefore that it could be that the presence of some heavy metals accumulated in the plants may have reached toxic levels thereby causing inhibition to their growth and pigment contents. The plant growth expressed as shoot and root dry weight of Atriplex plant was adversely inhibited when exposed to high concentrations of polluted soil. Significant increases in chlorophyll content were observed in leaves for three Atriplex varieties after the plants were exposed to stress treatments. The carotenoid and anthocyanin content also decreased. Red variety of Atriplex accumulated more anthocyanins in leaves than green and rosea ones. The lipid peroxidation increased, considerably at 100% polluted soil, which is a typical plant reaction to the oxidative stress. We proposed for the reduction state of photosynthetic parameters to be a useful tool in bioassay toxicity testing of metal polluted soil. These results demonstrate that heavy metal contamination of soil has adversely affected the photosynthetic parameters of annual Atriplex. The present study shows that exposure to heavy metals induced oxidative stress which was accompanied by growth inhibition, enhanced lipid peroxidation levels, increase content of chlorophyll, decrease content of carotenoids and anthocyanins. Finally, it was concluded that annual Atriplex has a high ability to tolerate Cu, Ni, Pb and Zn, so it might be a promising plant to be used for phytostabilization of metal contaminated soil.