The direct contribution of water spinach to the P removal attributed to the high P-uptake capacity of water spinach (Li et al., 2009). We could see from Fig. 4 that phosphorus content in every organ of water spinach was almost increased as time elapsed, and the average phosphorus assimilation rate was highest in stem, which is different from the change of nitrogen content in organs of water spinach. The results showed that water spinach could assimilate large amounts of phosphorus from water body, which might be the main mechanism for phosphorus removal by water spinach in aquatic water.