Screening,Identification And Verification Of Allelochemicals Used In Betel Nut Root Exudates To Relieve Pepper Continuous Cropping Obstacles

Betel nut intercropping can effectively alleviate continuous pepper cropping obstacles,which is related to the interaction between the two underground parts,especially the improvement of pepper rhizosphere microenvironment under the action of betel nut root exudates,but the specific active components and their mechanisms of action are still not yet available clear.This experiment intends to extract and identify the root exudates of pepper and betel nut by clarifying the best root exudates extraction method,and screen out the components in the root exudates of betel nut that are specific to the root exudates of pepper,and then add them after classification.It is further clarified that under continuous cropping soil cultivation,the effects of different specific components on pepper seed germination,seedling growth and development and soil microenvironment.The main findings are as follows:Four methods of hydroponic extraction,in-situ extraction,fresh soil extraction,and airdried soil extraction were used to collect and extract the root exudates of betel nut.After liquid quality analysis and identification,the number of metabolites was 438,401,369,and346,respectively,Hydroponic extraction method retains the most complete root exudates.On this basis,hydroponics was used to analyze the number of metabolites in the root exudates of pepper and betel nut,including 426 kinds of pepper and 438 kinds of betel nut.There are 509 different substances in the root exudates of the two and 329 different metabolites.With the increase of concentration,allelochemicals promoted germination firstly and then decreased,and the promotion effect was the strongest under the treatment of 100%concentration.The germination rate,germination vigor,germination index,vitality index and other indicators increased by 2.83% to 13.20%,9.52% to 44.45%,1.32% to 35.83%,6.62% to 65.48%,respectively.Among the different components,organic acids,phenolic acids,and flavonoids have significantly better effects on seed germination than amino acids and sugars.The overall performance of allelochemicals on the growth of pepper seedling plant height is "low concentration promotes,high concentration inhibits",so follow-up analysis is carried out at 100% concentration.Organic acids,phenolic acids,and flavonoids have the most prominent comprehensive promotion effect.The total root length of seedlings increased by 18.08% to 32.40%,the number of root tips increased by 11.04% to 36.82%,root malondialdehyde was reduced by 5.13% to 24.27%,and the leaf proline Acid decreases by11.91% to 39.73%;in addition,organic acids and flavonoids increase the net photosynthetic rate of seedling leaves by 46.01% to 49.30%,and the activity of superoxide dismutase increases by 40.77% to 53.48%.Organic acids and phenolic acids have an effect on peroxidation.Hydrogenase activity increased by 107.79% to 129.47%.Organic acids,phenolic acids,and flavonoids increase soil p H by 1.67% to 2.83%,reduce total nitrogen content by 18.86% to 22.37%,reduce total phosphorus by 4.17% to12.5%,and reduce available potassium by 24.38% to 44.69%,and nitrate reductase Decrease1.10% to 4.11%,oxidoreductase decrease 4.90% to 27.87,at the same time significantly improve the microbial carbon source utilization activity and diversity index of pepper rhizosphere soil,and increase the abundance of beneficial bacteria such as Pseudomonas and Bacillus.In summary,this experiment improved the soil microenvironment of continuous cropping pepper through the addition of different specific components,promoted the germination of pepper seeds and the growth of seedlings,alleviated the impact of continuous cropping obstacles on pepper,and organic acids,phenolic acids,and flavonoids in addition to being superior to adding root exudates directly,these specific components are also superior to amino acids and sugars.Therefore,adding organic acids,phenolic acids,and flavonoids during the continuous cropping of pepper can alleviate the obstacle of continuous cropping.This provides new theoretical basis and technical guidance for the production of continuous cropping pepper.