## 1 Introduction  
Glyphosate is the most widely used foliar-applied, non-selective herbicide against a broad range of different weeds. It causes nearly a direct growth inhibition, followed by chlorosis in young tissues and necrosis throughout the entire plant within 1-2 weeks after application. Glyphosate was evaluated as a toxicologically and environmentally safe chemical, because the mode of action is restricted to plants and some microbes. An accumulation in the environment is not likely to occur as a fast-microbial degradation was observed under optimum field conditions. Therefore, glyphosate became the \"world's best-selling herbicide\" after it was introduced in 1974 [1]. The application is of high relevance in no-till cropping systems and helps to reduce nutrient losses and erosion. Glyphosate application increased considerably when glyphosate-resistant, genetically modified crops were developed and which are nowadays grown in high proportions especially in the United States [2]. A further advantage of glyphosate application is the acceleration and synchronization of the ripening process of cereals that enable an economic harvest with lower losses. The mode of action of glyphosate is an inhibition of the enzyme 5-enolpyroyl-shikimate-3-phosphate synthase (EPSPS) in the shikimate pathway that is restricted to plants and microbes, wherefore negative effects on animals and humans seemed impossible. As a result, the biosynthesis of essential aromatic amino acids (tryptophane, phenylalanine, and tyrosine) is disturbed as well as the biosynthesis of molecules that are derived from these amino acids such as phytoalexins, lignin, indoleacetic acid, tannins, anthocyanins, and many other compounds. As a consequence, treated plants desiccate within a short while. Not only the reduction of aromatic amino acids is responsible for this effect but also an increased carbon flow to the shikimate pathway, because of missing feedback inhibition and subsequent shortage of carbon for other pathways [1]. Once taken up by the plants via the leaf's surface, glyphosate is quite mobile within the plant and reaches meristems, young roots and leaves, storage organs, and other growing tissue. According to [PERSON] and [PERSON] [1] the easy uptake, the excellent translocation to growing sites, nil or limited degradation in the plant, and a slow mode of action are the reasons for the excellent efficacy of glyphosate. In the last couple of years, a controversial discussion came up. There is an increasing body of evidence that the chemical is negatively affecting biodiversity and wildlife, and it is under suspicion of provoking cancer in humans [3]. Due to the fact that glyphosate resistance has become a standard ingredient in genetically modified crops, gene flow of glyphosate resistance transgenes to non-transgenic crops has occurred. As a result of the extensive use of glyphosate and the high selection pressure, naturally resistant weed crops have been developed in the last several years even if it took more than 20 years since glyphosate started being used [4; 5]. Already, more than 20 weed species have developed glyphosate resistance [5]. Moreover, data indicate that degradation of glyphosate is much lower in the northern hemisphere and translocation of glyphosate to non-target plants and to water bodies cannot be excluded [3]. The toxic effects of glyphosate and its degradation products have been described in bacteria and fungi [6] as well as in invertebrates and vertebrates in terrestrial and aquatic ecosystems [7; 8; 9; 10]. Aquatic systems are especially endangered because of the high solubility of glyphosate-based formulations, and the effects on several organisms are reviewed in [PERSON] et al. [3]. Despite the fact that the criteria for permission to use glyphosate in the EU were just recently elongated, member states can decide on their own whether glyphosate usage will be further allowed on a national level.