[Effects of Nitrate in Water on the Growth of Iris pseudacorus L. and Its Adsorption Capacity of Nitrogen in a Simulated Experiment].

In order to provide references for the application of emergent plants in the remediation and restoration of aquatic ecosystems, a hydroponic experiment was conducted for Iris pseudacorus L. with different nitrate mass concentrations (i. e., 10.68, 23.88, 42.22, 63.33, 82.92, 97.13 mg·L-1). The effects of nitrate mass concentration in water on the growth and nitrogen absorption capacity of I. pseudacorus were evaluated by the aboveground biomass, belowground biomass, root-shoot ratio, chlorophyll content, nitrogen uptake, and nitrate removal efficiency of the plants. The following results were obtained from the experiment. 1 The effects of nitrate mass concentration on the aboveground (stems and leaves) growth of the I. pseudacorus were greater than that on the belowground (roots) growth. Compared with the values before the experiment, the root-shoot ratio of the I. pseudacorus increased in the treatment with 10.68 mg·L-1 of nitrate mass concentration; while the root-shoot ratio decreased in the treatments with 42.22-97.13 mg·L-1 of nitrate mass concentration. 2 The I. pseudacorus grew better with nitrate mass concentration ranging from 23.88 mg·L-1 to 63.33 mg·L-1; and the chlorophyll biosynthesis of the plants was inhibited in the treatments with 10.68, 82.92, and 97.13 mg·L-1 of nitrate mass concentration. 3 The total nitrogen accumulation of the I. pseudacorus was in range of 10.56-75.43 mg in the experiment, which increased with the increase of nitrate mass concentration; and the accumulation of nitrogen in the belowground parts was 7.2, 2.3, 2.5, 2.1, 1.6, and 1.5 times of that in the aboveground parts, respectively. 4 The nitrogen utilization efficiency of the aboveground parts was higher than that of the belowground parts. 5 The removal rates of nitrate by I. pseudacorus were 94.9%-99.3%, which increased with increasing nitrate mass concentration. The nitrate mass concentration in water decreased with time in exponential function. In conclusion, I. pseudacorus has promising performance in the removal of nitrate in water, but its growth, nitrogen adsorption, and nitrate removal rate were significantly affected by the nitrate mass concentration. Moreover, the response of growth and nitrogen adsorption in aboveground of I. pseudacorus to nitrate mass concentration was more sensitive than that in belowground.