Effects Of Exogenous Phosphorus On Ginseng Quality And Soil Physicochemical And Biological Characteristics

Phosphorus is a component of a series of important compounds in plants,which participates in many physiological and biochemical reactions in plants.When plants are deficient in phosphorus,they show symptoms such as yellowing leaves,slow growth,decline in yield and delayed maturity.Ginseng is a perennial herb of Panax quinquefolium.Rational application of phosphorus can promote root development,accumulation of saponins and increase resistance of Panax quinquefolium.At present,there are few studies on rational application of phosphorus fertilizer.In view of this,three-year-old and two-year-old ginseng seedlings were studied in soil and water culture experiments,respectively.The effects of different phosphorus treatments on soil fertility and yield characteristics of ginseng and the transcriptome of ginseng leaves under phosphorus stress were studied in order to clarify the effects of phosphorus stress on the growth and development of ginseng.The results are as follows:1.Conventional agrochemical analysis was used to study soil characteristics and plant nutrients.Five concentrations of exogenous phosphorus were set up to treat the soil.: P0(0mmol/L)?P1(0.4 mmol/L)?P2(1 mmol/L)?P3(2.5 mmol/L)?P4(6.25 mmol/L).The results show that the application of phosphorus fertilizer significantly increased the content of total phosphorus and available phosphorus in soil and the activation coefficient of phosphorus in soil.The content of available potassium and nitrate nitrogen increased significantly.When the concentration of external phosphorus was 1-2.5mmol/L,ginseng yield increased by 17.07%,root activity was the highest,electrolyte permeability was lower,P,K,N,Ca,Fe and Mg contents in roots reached the maximum,which increased by 20.53%-66.88%,1.93%-52.61%,18.71%-38.59%,16.11%-38.57%,3.45%-52.54%,1.4%-23.7% respectively.2.Enzyme-catalyzed reaction and high-throughput sequencing technology were used to develop soil enzyme activity and microbial community structure composition: when phosphorus was insufficient or excessive,soil enzyme activity was decreased,but soil microbial quantity was increased,especially under phosphorus excess treatment(P4),the number of specific microorganisms was increased.Chao1,observed-species and Shannon index were the highest,which were 2950.40,9.61 and 3752.30,respectively.The dominant bacteria were the same under the treatment of phosphorus,but the status of functional microorganisms changed,such as Bacteroidetes and Gemmatimonadetes.Further redundancy analysis showed that soil pH value and acid phosphatase activity were the main factors affecting the evolution of microbial colonies.Twenty-two marker microorganisms were identified by LEfSe analysis at different classification levels which may be related to phosphorus stress.3.The results of water culture experiments on saponin content and nutrient migration at different growth stages showed that the above-ground Rb1,Rb2,Rb3,Rc and Rd contents increased significantly by 231.25%~256.25%,390.78%~514.47%,63.04%~117.39%,157.77%~222.22%,463.35%~375.77%compared with the non-phosphorus treatment.When the concentration of external phosphorus was 1mmol/L~2 mmol/L,the contents of Rb1,Rb2,Rb3,Rc and Rg1 in the underground reached the maximum,which were 0.445%,0.282%,0.043%,0.253% and 0.279% respectively.At flowering stage,the contents of Fe,Mg,Mn,Ca and Zn in underground part of Panax ginseng were higher than thoseabove ground,while those in green fruit stage were higher than those in underground part,while Fe,Mn and Zn remained mainly in underground part..4.Illumina Hiseq2500 was used to sequence the transcriptome of two-year-old ginseng leaves under phosphorus stress.A total of 429798772 raw read pairs were obtained.419529431 clean read pairs were obtained through quality control.5782 differential genes were identified.Functional enrichment analysis showed that phosphorus treatment can lead to differential gene expression of molecular function,biological process and cell components.Differential genes are enriched in terpenoid skeleton biosynthesis pathway and carotenoid biosynthesis pathway,which may be related to ginsenoside biosynthesis.