Effects Of Elevated CO₂ Concentration And Nitrogen Addition On Photosynthetic Characteristics And Fruit Quality Of Lycium Barbarum L.

In order to explore the effects of elevated atmospheric CO2 concentration and nitrogen addition on the growth,photosynthetic characteristics and main fruit quality of Lycium barbarum L.,the cuttings of one year old ’Ningqi-1’ were used as experimental materials,and the natural environment CO2 concentration(T1,380±20μmol·mol-1)and increased CO2 concentration(T2,760±20 μmol·mol-1)were set by open-top chamber control system.Three nitrogen levels(N0,0 g·kg-1 soil),(N1,1 g·kg-1 soil),(N2,2 g·kg-1 soil)were setted.The morphological index,photosynthetic index and main quality index were measured at 50 d,80 d,110 d and 140 d,respectively,and the changes of characteristic metabolites in ’Ningqi-1’ fruit were analyzed by metabonomics.The main results are as follows:1.Under the condition of increasing CO2 concentration,N0 and N1 treatments could promote the growth of ground diameter of ’Ningqi-1’,while N2 treatment could reduce the net growth of ground diameter of ’Ningqi-1’.The increase of atmospheric CO2 concentration and nitrogen addition promoted the growth of shoot length and shoot thickness of ’Ningqi-1’.The effect of N1 treatment on shoot thickness was more obvious,and the late stage of N1 treatment had a more significant effect on shoot length.2.Under the treatment of elevated atmospheric CO2 concentration,the activity of ribulose-1,5-bisphosphate carboxylase/oxygenase(RUBP)of ’Ningqi 1’ was at a high level throughout the growing season.During the peak growth period of summer fruit,the activity of fructose 1,6-bisphosphatase(FBP)was higher,and the chlorophyll content was higher at the level of N1 nitrogen addition.During the peak growth period of autumn fruit,under N1 treatment,the net photosynthetic rate and water use efficiency of ’Ningqi-1’ increased,the activities of rubisco activator(RCA)and phosphoenolpyruvate carboxylase(PEPC)increased,and the transpiration rate decreased.3.The increase of CO2 concentration and nitrogen addition increased the total sugar content of’Ningqi-1’ fruit,but decreased with the extension of treatment time,and the total sugar content of N1 treatment was the highest.In summer,the contents of total phenols and Lycium barbarum polysaccharides in ’Ningqi-1’ increased at first and then decreased,but in autumn,the contents of total phenols and Lycium barbarum polysaccharides were less affected by this environment.Under the condition of increasing CO2 concentration,the fruit shape index of ’Ningqi-1’ decreased with the increase of nitrogen application.The single fruit weight and yield of ’Ningqi-1’ summer fruit and autumn fruit increased under N1 treatment.4.The increase of CO2 concentration and nitrogen addition could effectively promote the absorption and utilization of underground nutrients by Lycium barbarum L.,and promote the decomposition and utilization of nitrogen in soil.The content of available nitrogen in soil under T2N2 treatment reached 64.50 mg·kg-1,at this time,plants also have a strong ability to absorb and utilize phosphorus.The content of available phosphorus in soil under T2N2 treatment was only 13.55 mg·kg-1,which was significantly lower than that of other treatments.Under normal CO2 concentration,nitrogen addition contributed to the absorption and transport of phosphorus by plants,and the increase of CO2 concentration and nitrogen addition could also effectively promote the absorption and utilization of soil phosphorus and soluble minerals by Lycium barbarum L.,but the change of environmental conditions had no significant effect on the absorption of potassium ions by plants,and the concentration of potassium ions among different treatments ranged from 197.42 mg·kg-1 to 206.82 mg·kg-1.5.The metabonomics of the fruit of ’Ningqi-1’ was analyzed,and a total of 3621 metabolites were annotated.The number of differential metabolites ranged from 52 to 259,and there were more differential metabolites between T1N2 VS T2N2 and T2N1 VS T2N2,which were 259,216 respectively.Under the condition of changing CO2 concentration and nitrogen addition,the synthesis and metabolism of ABC transporter,the biosynthesis of tryptophan,unsaturated fatty acid,aminosaccharide and nucleoside,the biosynthesis of carotenoids,diterpenoids,glucosinolates,indole alkaloids,isoquinoline alkaloids and phenylpropane metabolism were significantly affected.Under the condition of increasing CO2 concentration,the effects of different concentrations of nitrogen on the pharmacological components of ’Ningqi-1’ were different.Light nitrogen application could promote the synthesis of phenols such as myricetin,kaempferol,rutin and red bean saponins,while heavy nitrogen application could increase the contents of psoralen and cimicifolin in ’Ningqi-1’ fruit.