In general, TN removal by water spinach-uptake was mainly realized by increasing the tissue N content. From Fig. 4, it can be seen that the nitrogen content in root of water spinach was increased as time elapsed, but not significant increment was observed in stem and leaf, which illustrated that the nitrogen content might be transported from stem and leaf to root, and the stem of plants plays the effect of nutrient element transportation. In addition, plants adsorption might not be a main mechanism for nitrogen removal by water spinach in aquatic water.