Effects of N addition on photosynthetic characteristics and leaf senescence in Stipa bungeana of steppe grasslands in the Loess Plateau

In order to explore the effects of nitrogen (N) deposition on grassland plant metabolism function,this study conducted N fertilization addition on the Loess Plateau natural grassland by simulating nitrogen deposition and analyzed leaves N content, net photosynthetic rate(Pn), stomata conductance(Gs), transpiration rate(Tr), water use efficiency(WUE) and Chlorophyll content of Stipa bungeana on different N addition levels to explore the effects of nitrogen addition on photosynthetic characteristics and leaf senescence of S. bungeana. The results showed the N content, chlorophyll content, net photosynthetic rate and water use efficiency increased significantly with N addition. However, the stomata conductance and transpiration rate did not response to N addition remarkably. In addition, the chlorophyll degradation rate of S. bungeana was delayed by N addition. This paper revealed that nitrogen fertililization played primary roles in regulating photosynthetic characteristics and leaf senescence of S. bungeana, also appropriate nitrogen deposition could improve photosynthetic performance and delay leaf senescence of S. bungeana.