Arsenate, cadmium and lead affect the plant detoxification cascade for organic pollutants.

Multiple sites of moderate to low pollution with heavy metals or organic xenobiotics have been identified throughout Europe, and those where no immediate pressure exists for further use, may well be remediated by plant based technologies. Hence, phytoremediation has become a green sustainable technology that has gained increasing attention during the last decade. Municipal and industrial wastewater treatment plants can be optimized by the addition of lagoons with aquatic macrophytes. However, it is obvious, that quite a number of remediation projects failed due to insuf¬ficient plant performance. In this paper, we present evidence that Typha and Phragmites, two widely used plant species in phytoremediation, are capable of removal and metabolism of heavy metals and organic pollutants from water and sediments to some extent, but will fail at higher concentrations. We show also that pollution with heavy metals will interfere with both, the oxidative stress defence in plants, and with their ability to conjugate and detoxify organic xenobiotics. Despite plant species dependent differences, the general reactions seem to include oxidative stress and an induction of antioxidative enzymes. Both species respond to trace elements with oxidative stress and decay of central physiological functions. In non-hyperaccumulators like the chosen species, photosynthesis, growth, but also defense will cease at higher concentrations or prolonged exposure to heavy metals. Interestingly, defense reactions against organic xenobiotics, so far considered unrelated to heavy metal stress will also be impaired by mixed pollution, especially cadmium. Here, direct interac¬tions with enzyme proteins are possible, but influence on transcription is frequently observed. For the practical use of plants in phytoremediation, it is discussed that only species with proven stress resistance or mixed plant consortia with differential resistances and uptake can be recommended