## 1 Introduction  
Phytoremediation is a technique that utilizes plants to remove or transform toxic chemicals incorporated in soils, ground water, and surface water. Various plants are used for removal or degradation of inorganic and organic contaminants, such as pesticides, antibiotics, heavy metals, and nutrients.  
Phytoremediation techniques are used extensively because they have a number of advantages. Phytoremediation is low cost compared with conventional techniques and is suitable for treating very large land areas [1]. Furthermore, these techniques may be more effective than conventional techniques based on chemical extraction because the use of plants for environmental cleanup does not cause secondary pollution. However, phytoremediation also has limitations. A significant disadvantage of phytoremediation by aquatic plants is their shallow root systems, which limit the depth of soil treatment by the rhizosphere. Another disadvantage is the slow rate of environmental cleanup, which may take more than 10 years [2]. Phytoremediation effectiveness decreases during winter, and plant diseases or pests may occur in the condition of plant damage [3].  
For decades, a wide variety of antibiotics has been extensively applied worldwide for preventing or treating human, animal, and plant infections and as feed additives for animals to prevent or treat diseases and promote growth [4]. Consumption of veterinary antibiotics has been increasing in both industrialized and developing countries. However, in Korea, the total production of antibiotics decreased significantly from 1500 tons in 2007 to 820 tons in 2013. This dramatic reduction in use of veterinary antibiotics was due to restrictions on their use for feed supplementation. Tetracyclines, sulfonamides, and penicillin are the most commonly used antibiotic types, with usage of 165, 60, and 160 tons, respectively, in 2014. These antibiotics are commonly found in both aquatic and agricultural environments, associated with the discharge of wastewater to the environment. Despite the low concentrations usually found in water ecosystems (from nanograms to micrograms per liter), continuous discharge of antibiotics and their degradation products through different pathways makes them 'pseudo-persistent' in the environment [5].  
Macrophytes accumulate pollutants by incorporating them into the structures of their cells. In addition, these plants have a natural ability to absorb and metabolize xenobiotics while adapting to harsh conditions in a contaminated environment [6]. Some studies have used aqueous solution amended with different antibiotics to address plant uptake. The water plants _Myriophyllum aquatic_ (parrot feather) and _Pistia stratiotes_ (water lettuce) were previously used for the study of phytoremediation of tetracyclines and oxytetracyclines in aqueous media [7]. Comparable levels of antibiotic removal by filtered root exudates from these two species a suggested involvement of root-secreted enzymes/metabolites in degrading/transforming the antibiotics [7].  
The aim of the present study was to investigate the accumulation of antibiotics in two kinds of plants and to survey the phytotoxicity of antibiotics. The study was performed under hydroponic culture conditions to avoid potentially confounding effects of adsorption of antibiotics on soil particles [8]. The hydroponic culture solution contained a mixture of three commonly used antibiotics in South Korea: norfloxacin, sulfamethazine, and tetracyclines.