The Effect of Different Combinations of Nitrogen Forms on Growth and Physiological Traits of Ryegrass under Cd Stress

【Objective】 Nitrogen exists in different forms which have different effects on soil biogeochemical processes and plant growth and nutrients acquisition. The purpose of this paper is to investigate the impact of combinations of different nitrogen forms on the growth and physiological traits of ryegrass in hydroponic culture under Cd stress. 【Method】 We used treated wastewater as the hydroponic culture and grew the ryegrass by contaminating the culture with Cd concentration set at 0.01 and 0.1 mg/L, respectively. The nitrogen was nitrate and ammonium with the nitrate : ammonium ratio being set at 100∶0, 75∶25, 50∶50, 25∶75 and 0∶100. In each treatment, we measured the physiological traits of the plant 【Result】 When the Cd concentration was 0.01 mg/L, increasing nitrate application promoted the growth of both roots and shoots, as well as absorption of Cd by the ryegrass when the nitrate : ammonium ratio increased from 25% to 100%. When Cd concentration increased to 10 mg/L Cd, the MDA content in the ryegrass was lower than that at 0.01 mg/L concentration, regardless of the nitrate : ammonium ratio. The content of MDA in the ryegrass under Cd stress was the lowest when nitrate : ammonium was 100∶0. We also found that Cd stress boosted the activities of CAT and POD in the ryegrass when the amount of ammonium increased from 50% to 100%. 【Conclusion】 Increasing ammonium in the nutrient solution benefited Cd2+ absorption by the ryegrass, thereby reducing its detrimental impact on ryegrass growth and development.