Responses Of Antioxidant Properties Of Dominant Species In Swamp Meadows In The Source Region Of The Yangtze River To Simulated Warming And Nitrogen Addition

Temperature is an important environmental factor that affects the growth and development of plants.As the global greenhouse effect intensifies,the rising temperature will have a great impact on plant physiology.At the same time,the process of human industrialization has greatly increased the production and emission of nitrogen,which has prompted the atmospheric nitrogen deposition to intensify and spread to the whole world,thus affecting the natural circulation of nitrogen,threatening the health and safety of the global ecosystem.As the main organs of plants,the changes of physiological indexes of leaves and roots have an important impact on plant growth and development.Roots,leaves and their functional traits will adapt to environmental changes by weighing relationships or synergistic effects,so that plants can adopt corresponding physiological response strategies to maintain growth.In order to explore the effects of warming and nitrogen addition on the antioxidant characteristics of main plants in alpine swamp meadow of Qinghai-Tibet Plateau,this study adopted open-top chambers system to simulate warming and exogenous nitrogen addition,taking Kobresia humili,Kobresia tibetica and Carex Moorcroftii as the research objects,and measured the antioxidant characteristics of leaves and roots of three plants under different warming and nitrogen addition.The sensitivity of each index to different treatments was analyzed.The results show that:(1)Under the warming treatment,the malondialdehyde content in the leaves and roots of the three plants generally showed a downward trend.Proper warming promoted the growth of plants and alleviated the oxidative damage of plants.Under the warming treatment,the activities of superoxide dismutase,peroxidase,catalase,glutathione reductase and ascorbate peroxidase in Kobresia humili and Kobresia tibetica generally showed an upward trend,but the activities of peroxidase and catalase in the roots of the two plants showed a downward trend.The activities of superoxide dismutase,glutathione reductase and ascorbic acid peroxidase in Carex Moorcroftii showed an upward trend,while the activities of peroxidase and catalase showed a downward trend.Warming increased the content of flavones and carotenoids in three plants,increased the content of ascorbic acid in Kobresia humili,reduced the content of reduced glutathione,increased the content of reduced glutathione in Kobresia tibetica and Carex Moorcroftii,and reduced the content of ascorbic acid.(2)The content of malondialdehyde in leaves and roots of three plants decreased under nitrogen application,but the content of malondialdehyde in leaves and roots of Kobresia humili and Carex Moorcroftii increased under high nitrogen application.Nitrogen application increased the activities of superoxide dismutase,catalase,glutathione reductase and ascorbate peroxidase in three plants,At the same time,catalase activity was higher at low nitrogen level,and ascorbic acid peroxidase activity was higher at high nitrogen level.After nitrogen application,there were some differences in antioxidant enzyme activity among different organs of three plants,but the antioxidant enzyme activity showed an overall increasing trend.Nitrogen application increased the contents of ascorbic acid and flavones in Kobresia humili,the contents of reduced glutathione and carotenoids were decreased,the contents of ascorbic acid,flavones and carotenoids in Kobresia tibetica and Carex Moorcroftii were increased,and the contents of reduced glutathione were decreased.(3)Under the treatment of warming and nitrogen application,malondialdehyde content in leaves and roots of Kobresia humili decreased at first and then increased,while malondialdehyde content in Kobresia tibetica and Carex Moorcroftii fluctuated,the content of malondialdehyde in the three plants was lower than that of the control.The activities of superoxide dismutase,catalase and glutathione reductase in three plants were increased by warming and nitrogen application.There was no obvious change trend of peroxidase activity in three plants,but the peroxidase activity in Kobresia humili was significantly higher than that in other plants.The activity of ascorbic acid peroxidase in Kobresia humili and Kobresia tibetica leaves decreased significantly under low temperature and low nitrogen treatment,but increased significantly under high temperature and high nitrogen treatment.The ascorbic acid content of three plants mainly increased at first and then decreased,the content of reduced glutathione began to increase under high temperature and high nitrogen treatment,and the content of carotenoids and flavones mainly showed an increasing trend.The contents of antioxidant indexes in leaves of the three plants are higher than those in roots,and plant leaves play an important role in maintaining the balance of active oxygen in vivo.(4)Sensitivity analysis shows that different plants and organs have different sensitivities to different treatments.Most of the antioxidant enzyme activities in the three plants are most sensitive to nitrogen application only,and the antioxidant content is most sensitive to temperature increase combined with nitrogen application,which indicates that the antioxidant enzyme activities in the three plants are more affected by nitrogen application.However,the antioxidant content is more affected by the interaction of increasing temperature and applying nitrogen.