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The accumulation and excretion of lead (Pb) and cadmium (Cd) by salt cedar (Tamarix smyrnensis Bunge) were investigated in this study. Tamarix smyrnensis plants were exposed to the mixtures of Pb and Cd and high salinity for 10 wk. Subsequently, Pb and Cd uptake was quantified in the shoots and roots of the plants by ICP-AES. In addition, physiological parameters such as biomass production, shoot length, plant appearance, and chlorophyll content were examined. The roots accumulated the highest amount of Pb. Salinity was found to not have an important effect on Pb translocation to the leaves. Cd was translocated into the aerial part in a higher portion than Pb. Cd content in leaves of T. smyrnensis increased with the increasing salinity. The visible toxicity symptoms, if present, were connected only to the high salinity. The excretion of Pb and Cd by salt glands was observed and quantified. T. smyrnensis excreted a significant amount of metals on the leaf surface. This characteristic of salt cedar plants can be viewed as a novel phytoremediation process for the remediation of sites contaminated with heavy metals that we have termed "phyto-excretion."

Physiological responses of Matricaria chamomilla plants exposed to cadmium (Cd) and copper (Cu) excess (3, 60, and 120 lM for 7 days) with special emphasis on phenolic metabolism were studied. Cu at 120 lM reduced chamomile growth, especially in the roots where it was more abundant than Cd. Notwithstanding the low leaf Cu amount (37.5 lg g 21 DW) in comparison with Cd (237.8 lg g 21 DW) at 120 lM, it caused reduction of biomass accumulation, F v /F m ratio and soluble proteins. In combination with high accumulation of phenolics, strong reduction of proteins and high GPX activity in the roots, this supports severe redox Cu properties. In terms of leaf phenylalanine ammonia-lyase (PAL) activity, it seems that Cd had a stimulatory effect during the course of the experiment, whereas Cu was found to stimulate it after 7-day exposure. The opposite trend was visible in the roots, where Cd had a stimulatory effect at high doses but Cu mainly at the highest dose. This supports the assumption of different PAL time dynamics under Cd and Cu excess. A dose of 60 and 120 lM Cu led to 2-and 3-times higher root lignin accumulation while the same Cd doses increased it by 33 and 68%, respectively. A Cu dose of 120 lM can be considered as limiting for chamomile growth under conditions of present research, while resistance to high Cd doses was confirmed. However, PAL and phenolics seemed to play an important role in detoxification of Cd-and Cu-induced oxidative stress. # 2008 Wiley Periodicals, Inc. Environ Toxicol 23: 123-130, 2008

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