Study On Key Enzyme Activities Of Nitrogen And Chlorophyll Metabolic Pathways In Leaf Senescence Process Of Zoysiagrass

Lawns are an important part of urban greening.Zoysiagrass is one of the excellent warm-season lawn grasses.They have the characteristics of drought resistance,trample resistance,and wear resistance.When the temperature was law in fall,green fading and yellowing has seriously affected the quality of turf lawns,and also greatly limited their application in northern areas.Therefore,studying the changes in nitrogen metabolism and chlorophyll metabolism of Zoysiagrass during aging can lay a scientific basis for revealing the regulation mechanism of nitrogen metabolism and chlorophyll metabolism of Zoysiagrass,and then provide a theory for the subsequent study on extending the green period of Zoysiagrass basis.In this study,Zoysia tenuifolia,Zoysia matrella and Zoysia japonica were introduced from the United States and Hubei,Shanghai,Shandong,Beijing,Liaoning and other places were used as experimental materials,and six treatments with different light,temperature and treatment time were set to simulate the natural cooling process.By measuring the changes of the nitrogen content,the key enzyme activities of nitrogen metabolism,the chlorophyll content,the synthetic precursors content and the activities of enzymes related to chlorophyll metabolism of the plant leaves during senescence,determined the physiological characteristics of leaf nitrogen metabolism and chlorophyll metabolism from the physiological level during the senescence of Zoysia japonica.The main findings were as follows:(1)With the progress of the treatment aging process,the ammonium nitrogen content of 11 parts of Zoysiagrass material showed a significant increase trend.Zoysia tenuifolia collected from Hubei and the United States(No.3,No.4),The nitrate nitrogen content of Zoysia japonica(No.9and No.11)from Liaoning and Zoysia japonica(No.10)from Jilin increased significantly(P<0.05).The nitrate nitrogen content of Zenith(No.1),Meyer(No.2),Zoysia grosvenori(No.5),Zoysia japonica(No.6)from Shanghai,Zoysia japonica(No.7)from Shandong and Zoysia japonica(No.8)from Liaoning were significantly reduced(P <0.05).The soluble protein content of Zoysia tenuifolia(No.3,No.4)from the United States and Hubei,Zoysia matrella and Zoysia japonica from Shanghai(No.5 and No.6)and Zoysia japonica(No.11)in Liaoning increased significantly(P <0.05).The soluble protein content of Zenith(No.1),Meyer(No.2),and Zoysia japonica(No.7)from Shandong,two parts of Zoysia japonica(No.8 and No.9)from Liaoning and Zoysia japonica(No.10)from Jilin decreased significantly(P <0.05).The activity of nitrogen metabolism related enzymes NR and GS of Zoysia japonica material was significantly increased,and the activity of GOGAT increased at a lesser degree,which resulted in the weakening of nitrogen metabolic activity and chlorotic performance of Zoysia japonica.(2)With the progress of the treatment aging process,the chlorophyll content of 11 parts of Zoysiagrass material showed a gradual decrease trend,while the carotenoid content gradually increased,but in treatment VI(day / night 0 /-5 ℃,8 h light,1000 Lx),its content showed a downward trend;the reason for the decrease of chlorophyll content during the aging process of 11 parts of Zoysiagrass materials was: Zenith(No.1)and Zoysia matrella(No.5)collected from Shanghai were Due to the accumulation of PBG and Coprogen III content;Meyer(No.2)and Zoysia japonica(No.8)from Liaoning are due to the accumulation of PBG,Proto IX and Pchlide content;American Zoysia tenuis(No.3)Chlorophyll synthesis is blocked due to accumulation of Pchlide content;Zoysia tenuifolia(No.4)collected from Hubei is due to accumulation of Mg-Proto IX and Pchlide content;Zoysia japonica(No.6)collected from Shanghai and Shandong Zoysia japonica(No.7)is the accumulation of PBG content;Zoysia japonica(No.9)collected from Liaoning and Zoysia japonica(No.10)is collected from Liaoning due to the accumulation of PBG and Pchlide content of Zoysia japonica(No.11)is due to the inhibition of ALA synthesis and the accumulation of PBG content caused by chlorophyll content decreased.The decrease in UROS and PPOX activity,the increase in UROD activity in the chlorophyll synthesis pathway,and the increase in Chlase and MDCase activities in the chlorophyll degradation pathway are the main reasons for the decrease in the chlorophyll content of 11 Zoysiagrass materials.Analysising all indexes of the 11 parts of Zoysiagrass material in the treatment V(day / night0 /-5 ° C,8 h light,1000 Lx light),we could find that during the aging process,the soluble protein of 11 parts of Zoysiagrass materials showed different trends due to different materials.The activity of NR and GS increased to a greater extent,while the increase of GOGAT activity was lower than that of GS,which affected the GS / GOGAT cycle.Ammonium nitrogen accumulated more and nitrate nitrogen is reduced or increased to a lesser extent than ammonium nitrogen,which ultimately leads to weakened nitrogen metabolism and promotes plant senescence,showing chlorosis and reduced chlorophyll content.The common obstruction of the chlorophyll synthesis pathway of 11 materials was accumulation of bile pigmentogen(PBG)and reduceing of uroporphyrinogen III synthase(UROS)activity,as well as Chlase and MDcase activities in the degradation pathway were significantly increased.Therefore,the reduction of chlorophyll content during the aging process of Zoysiagrass was due to the slowdown of nitrogen metabolism and obstruction of chlorophyll synthesis and degradation acceleration.