Studying the effects of different nitrogen application rates on the growth of elm seedlings under drought stress can provide a theoretical basis for the rational application of nitrogen fertilizer during dry sea-sons and alleviate the impact of drought stress on seedling growth.The experiment was conducted under pot-ted conditions,with normal water supply conditions as the control(CK),and five treatments were set up:drought stress(T1),nitrogen application rate of 8 g/plant(T2),16 g/plant(T3),and 24 g/plant(T4)under drought conditions.The results showed that:(1)Drought stress significantly reduced various growth indicators of elm seedlings,and the application of nitrogen fertilizer could effectively alleviate the impact of drought stress on seedling growth.With the increase of nitrogen fertilizer application,various growth indicators showed a trend of first increasing and then decreasing,and T3 treatment had the best effect;(2)Under drought stress,the activities of SOD,POD,and CAT in elm seedlings are enhanced.Applying nitrogen fertilizer can signifi-cantly increase the activities of antioxidant enzymes(SOD,POD,CAT)in elm seedlings under drought stress.The difference between T2 and T1 treatments was not significant,while T3 treatment was significantly higher than T1.The difference between T4 and T3 was not significant,indicating that T3 treatment can effectively im-prove antioxidant enzyme activity,but excessive application does not enhance the effect.The changes in antioxi-dant enzyme activity vary under drought stress,and the application of nitrogen fertilizer will showed a trend of first decreasing and then increasing SOD activity over time.POD showed a trend of first increasing and then decreasing,with the highest activity observed in all treatments in July.CAT activity gradually decreases over time;(3)Drought stress leads to a decrease in nitrate reductase activity and an increase in soluble protein con-tent in elm seedlings.After applying nitrogen fertilizer,nitrate reductase activity and soluble protein content in-creased,with T3 treatment showing the most significant effect.Comprehensive analysis suggests that T3 treat-ment(16 g/plant)was the appropriate nitrogen application rate for elm seedlings under drought stress.
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