Responses induced by high concentration of cadmium in Phragmites australis roots.

Cadmium is an important environmental pollutant with high toxicity to plants. We report the effects of high-dose Cd (100 micro M for 21 days) on the root apparatus of Phragmites australis plants, which are characterized by elevated water detoxification capacity and widely used in phytoremediation programmes. The examination of root sections by light and electron microscopy failed to reveal any significant cadmium-induced structural or ultra-structural modifications. However, histochemical localization of Cd disclosed accumulation of the metal in the parenchyma cells below the exodermis. Phytochelatins (PC) are thiol-rich peptides whose synthesis is induced by a range of metals. Our results indicate that total PC production increases after exposure to Cd, which suggests a pivotal role for phytochelatins in the sequestration of metal. Cd treatment also induced lignin deposition and marked stimulation of root antioxidant systems, suggesting that, because of its ability to adopt different strategies against the harmful effects of cadmium, Phragmites australis is a plant with high detoxification potential.