Effects Of Water And Nitrogen Coupling On Growth And Physiological Characteristics Of Poa Pratensis

Lawn plays an important role in the greening and beautification of urban and rural environment.Poa pratensis is one of the excellent cold-season turfgrass,which is widely used as lawn planting materials in residential areas,sports fields,parks,and both sides of roads.However,in order to maintain a good quality of the landscape and the use of lawn,people need to apply a large amount of nitrogen fertilizer and water,which will cause the waste of soil nitrogen resources and eutrophication of water body.In this experiment,17 overseas cultivars including Blue Ghost,Geronimo,Martha,Comet,Heidi,Bandera,Camas,Action,Rhythm,Merit,Impact,Blue Moon,Everest,Jackrabbit,Fielder,Park and Beyond and 3 wild populations in Qinshui County,Hunyuan County and Yingxian County of Shanxi Province are adopted,using split design,we set up two nitrogen treatments N1: 10 g·m-2,N2: 40 g·m-2and two water treatments W1: 60% ET,W2: 100% ET to study the change rule of the growth and development,photosynthetic characteristics and key enzymes of nitrogen metabolism in the water-nitrogen coupling process of Poa pratensis,and reveal the strategies of different types of Poa pratensis to adapt to low nitrogen and drought.The main results are as follows:The indicators of Poa pratensis measured at different nitrogen levels at 60% ET were significantly different.The fresh weight and dry weight of the grass clippings of Rhythm and Fielder under N2 treatment,the root volume,dry weight and root vigor of Comet,Rhythm and Beyond,were significantly higher than that of N1 treatment;the chlorophyll a content of Camas and Beyond under N2 treatment was significantly higher than N1 treatment;the total nitrogen,nitrate nitrogen and ammonium nitrogen content of Hunyuan,Bandera,Action,Rhythm,Park and Beyond and the nitrate reductase,glutamine synthetase and the activity of glutamate synthase of Heidi,Merit,Jackrabbit,Fielder and Park under N2 treatment was significantly higher than that of N1 treatment.The indicators measured at different nitrogen levels under 100%ET are also different.The root volume of Qinshui,Camas,Rhythm,Merit and Jackrabbit under N2 treatment,the total nitrogen,nitrate nitrogen and ammonium nitrogen content of 16 materials except Yingxian population,Comet,Jackrabbit and Fielder were significantly higher than that of N1 treatment.From the above,under low water treatment,the biomass,photosynthetic characteristics and key enzyme activities of nitrogen metabolism of Poa pratensis were significantly increased with the increase of nitrogen application rate,which had a positive effect on plant growth and the accumulation of dry matter.Under the condition of sufficient soil moisture,the content of different forms of nitrogen in the leaves of Poa pratensis was positively correlated with nitrogen addition.The indicators measured at different levels of low-nitrogen evapotranspiration of Poa pratensis are different.The net photosynthetic rate of Bandera,Rhythm,Blue Moon and Everest under W2 treatment was significantly higher than that under W1 treatment;the total nitrogen content of Camas and Park under W2 treatment was significantly higher than that under W1 treatment,with the increase of 22.35% and 52.15%;the nitrate nitrogen of Geronimo and Hunyuan,the glutamine synthetase and glutamate synthase activities of Blue Ghost,Geronimo,Martha,Heidi,Bandera,Action,Fielder and Park were significantly higher than those under W1 treatment.There are differences in the various indicators measured at different evapotranspiration levels of normal nitrogen.The root volume and dry weight of all materials except Comet,Heidi,Merit,Beyond under W2 treatment are higher than that under W1treatment;The content of total nitrogen,nitrate nitrogen and ammonium nitrogen of 15 materials except population of Yingxian and Hunyuan,Merit,Fielder and Beyond under W2 treatment and the nitrate reductase and glutamine synthetase activities of 20 Poa pratensis were significantly higher than those under W1 treatment.From the above,under low nitrogen conditions,with the increase of soil moisture,the activities of key enzymes in nitrogen metabolism of Poa pratensis are also increased,but there are little effect on biomass,photosynthetic characteristics and nitrogen content of different forms.Under normal nitrogen supply,the content of different forms of nitrogen and the activities of key enzymes in nitrogen metabolism increase with the increase of water supply.Using the membership function method in fuzzy mathematics to comprehensively evaluate20 materials with different water and nitrogen treatments,the results show that the tolerance of each material to drought and low nitrogen is as follows: Rhythm>Heidi>Martha>Fielder>Merit>Geronimo>Comet >Qinshui>Jackrabbit>Bandera>Everest>Impact>Blue Ghost>Park>Beyond>Action>Hunyuan>Blue Moon>Yingxian>Camas.In summary,through the comparative analysis of the 4 water and nitrogen treatments of20 Poa pratensis materials,we have selected the Poa pratensis species and populations that still perform well under the conditions of low maintenance costs(low nitrogen and drought),which provide theoretical basis for the breeding and scientific management of Poa pratensis.