Research On The Physiological And Biochemical Response Of Leymus Chinensis In Different Phenotypes To Nitrogen Deposition And Salt Stress

Leymus chinensis is a kind of grass species,which is tolerant to cold,drought,salinity and so on.It is an important forage resource because of its rich protein and high quality.L.chinensis is widely distributed in different soil types,due to the long-term adaptation to different growing environments,the morphological differences between L.chinensis under different growth conditions resulted in the differentiation of different phenotypes of L.chinensis.There were few studies on the physiological differences among different phenotypes of Leymus chinensis.Therefore,different phenotypes of L.chinensis were studied in this paper.The experiment was carried out in the Botanical Garden of Liaoning University from 2015 to 2016.By artificial simulated nitrogen deposition and saline-alkali stress environment to see the responses of different phenotypes of L.chinensis to nitrogen deposition and salinity stress.The effects of different phenotypes of L.chinensis on nitrogen and saline-alkaline environment were also analyzed.The results provide a theoretical basis for the protection of L.chinensis in nitrogen deposition and salinity stress.To protect the important forage resources L.chinensis the study is of great significance.The main results we obtain are as follows:1.Physiological response of different phenotypes of L.chinensis to nitrogen deposition has showed that the physiological and biochemical indexes of 8phenotypes were different when suffer to three nitrogen treatments.The effects of different phenotypes and nitrogen treatments on most of L.chinensis parameters were significant(P<0.05)or highly significant(P<0.01).The height of the different phenotypes of L.chinensis increased linearly with the increase of nitrogen treatment level,and the phenotype 4 and 7 showed a linear increase of y = a + bx and significant correlated.The order of plant height of the eight phenotypes of L.chinensis from high to low was almost the same at each nitrogen treatment level: 3>1> 9> 13> 7> 12> 4> 8,demonstrated that the shape of 8 phenotypes are different.The aboveground and underground biomass of 8 phenotypes of 8 phenotypes wassignificantly affected by nitrogen treatment level,the aboveground and underground biomass of phenotypes 8 and 9 L.chinensis decreased under high nitrogen treatment.For the protein content,NR,GS,and GDH activities,the results showed that the phenotypes 1 、 8 and 9 decreased when treated with high nitrogen.However,the phenotypes 4 and 7 had a significant increase with the increasing nitrogen treatment.Three phenotypes were damaged in different degrees,as the other five phenotypes of L.chinensis to nitrogen deposition were more tolerant.The results showed that the adaptability of 4,7,12 phenotypic L.chinensis to high concentration of nitrogen was stronger,and 8,9 were relatively weak.According to the study of the soluble protein content and the activity of nitrogen cycle related enzymes,the protein content,NR,GS and GDH activities of the 1,8 and 9 phenotypes decreased in the high nitrogen treatment.However,The activity of L.chinensis of phenotypes 4 and 7 was improved,it was proved that the adaptability of 4,7 phenotypes of L.chinensis on nitrogen were stronger,and the adaptability of 1,8,9 phenotypes of L.chinensis were weak.The analysis of photosynthetic indexes such as maximum net photosynthetic rate showed that the high concentration of nitrogen deposition reduced the maximum net photosynthetic rate of phenotype 1,3,9 and 13.For phenotype 9 of L.chinensis,the productivity and the internal physiological reaction were the most affected by high nitrogen treatment,which showed the adaptability to nitrogen deposition was the weakest.The phenotype 4,7,12 L.chinensis adaptability to nitrogen deposition is relatively stronger.The above results showed that among eight phenotypes of L.chinensis,phenotype 4,7 and 12 had a stronger adaptability to nitrogen deposition,but 1,8,9 phenotypes were weak relatively.2.The physiological responses of different phenotypes of L.chinensis to salt-alkali stress showed that the physiological and biochemical indexes of different phenotypes of L.chinensis changed significant(P <0.05)or extremely significant(P<0.01)to different degrees under the condition of four salinity treatments.The water content of four phenotypes of L.chinensis leaves changed with the increase of salinity treatment.The phenotype 1 、 4 and 8 of L.chinensis increased firstly and then decreased with the increasing of salinity stress,however,phenotype 7 was increasedwith the enhancement of salt concentration.The soluble sugar content of four phenotypes of L.chinensis increased linearly with the increase of stress intensity(R21=0.505,P<0.01;R24=0.405,P<0.01;R28=0.432,P<0.01;R27=0.141,P<0.05).The content of proline in L.chinensis was significantly different among the four phenotypes.The content of proline was the highest in phenotype 7 at each salinity treatment level.The activity of seven antioxidant enzymes(SOD,POD,CAT,APX,GR,DHAR,MDHAR)increased with the increase of salt stress in all four phenotypes,and most of them showed the increase linearly of y = a + bx,and a significant correlation was found.At each treatment level,except CAT and POD,the remaining five antioxidant enzymes among different phenotypes of L.chinensis from large to small in orders are: 7> 8> 4> 1,the above results showed that L.chinensis of phenotype 7 was better adapted to salt stress than other three phenotypes of L.chinensis.However,the phenotype of 1 was the weakest for salt stress...