Photosynthetic Physiological Response Of Three Species Of Leymus Chinensis Under Nitrogen Addition And Salinity-alkali Stress

Leymus chinensis is a perennial rhizome of gramineae,which has the characteristics of cold tolerance,drought tolerance,salt tolerance and so on.L.chinensis has high content of protein,mineral and carbohydrate,and has high feeding value.L.chinensis grows in different soil types,in the process of long-term adaptation to different growth regions or different soil types in the same region,L.chinensis populations with different leaf colors are formed.In the distribution area of L.chinensis,we can often see grey-green and yellow-green L.chinensis,and there are transitional leaf color L.chinensis.At present,there is still a lack of in-depth studies on the differences in photosynthetic physiological responses among the three leaf colors of L.chinensis.Therefore,this paper takes grey-green,transition color and yellow-green L.chinensis as the research object,and artificially simulates nitrogen deposition environment and saline-alkali stress environment,the photosynthetic physiological response of three species of L.chinensis was systematically studied to explain the adaptation of L.chinensis with different leaf colors,which is of great significance to the protection of L.chinensis,an important forage resource.The photosynthetic seasonal dynamic characteristics and photosynthetic physiological response of three species of L.chinensis to nitrogen addition under natural conditions showed that there were obvious seasonal differences in photosynthetic indexes of leymus chinensis.P_n,G_s,C_i,T_r and WUE all showed an overall trend of increasing first and then decreasing from May to September,in which P_n,G_s,C_i and T_r reached the maximum value in July,while WUE reached the maximum value in August.Under the three nitrogen treatment levels,the photosynthetic physiology and growth indexes of the three species of leymus chinensis were different,and according to the results of variance analysis,most of the indexes reached the significant(P<0.05)or extremely significant(P<0.01)levels.For the growth and physiological indexes of L.chinensis:plant height,plant number,aboveground and underground biomass,chlorophyll a content,chlorophyll b content,total chlorophyll content,carotenoid content,chlorophyll a/b,RUBPC activity,PEPC activity,GO activity and photosynthetic indexes:Pn,Gs,Tr,Ci and WUE were increased to different degrees under nitrogen treatment compared with the control group.Under the same nitrogen application concentration,most of the indicators among the three leaf colors showed the tendency of gray-green>transition color>yellow-green.According to the photosynthetic physiology and the response of growth indexes of the three leaf colors of L.chinensis to nitrogen treatment,the grey-green L.chinensis was the best,followed by transitional L.chinensis,and the yellow-green L.chinensis was the weakest.The experimental results of photosynthetic seasonal dynamic characteristics and photosynthetic physiological response of three species of L.chinensis to saline-alkali stress under natural conditions showed that the photosynthetic indexes of L.chinensis showed obvious seasonal differences.From may to September,Pn,Gs and Tr showed an overall trend of rise and then decline,while Ci and WUE showed an overall trend of rise.The photosynthetic physiological response of three species of L.chinensis to saline-alkali stress showed as follows:the photosynthetic physiology and growth indexes of the three species of L.chinensis were changed to different degrees at the four saline-alkali treatment levels,according to the results of anova,most of the indicators reached the level of significant(P<0.05)or extremely significant(P<0.01).The plant height,aboveground and underground biomass,RUBPC activity,PEPC activity and GO activity of the three species of L.chinensis decreased with the increase of salinity stress treatment intensity;plant number,chlorophyll a content,chlorophyll b content,total chlorophyll content and carotenoid content increased first and then decreased under saline-alkali stress;chlorophyll a/b showed the tendency of increase.In terms of photosynthetic parameters,P_n,G_s,C_i and T_r of the leaves of L.chinensis showed a decreasing trend under saline-alkali stress and the WUE of the three leaf color L.chinensis showed an increasing trend under saline-alkali stress.The Pnmax,LSP and AQY of the three leaf color L.chinensis showed an overall trend of gradual decline with the increase of salinity stress concentration,while the LCP and R_d showed an increasing trend.At the same saline-alkali concentration,most of the indicators among the three leaf colors of leytenia chinensis showed grey-green>transition color>yellow-green.The three species of L.chinensis showed strong adaptability under salt and alkali stress.The grey-green L.chinensis was the best,followed by the transitional L.chinensis and the yellow-green L.chinensis.