Effect Of Lavender Root Exudates From Yili River Valley On Growth-Promoting Activity Of ACC Deaminase-Producing Bacteria In The Rhizosphere

[Objective] This paper aims to investigate the interaction between root exudates,ACC deaminase activity,rhizobacteria,and growth-promoting ability at both the molecular level and with high-throughput sequencing technology.The goal is to establish a methodological basis for detecting the growth-promoting effects of root exudates and ACC deaminase activity in rhizobacteria.[Methods] Firstly,a multi-medium enrichment method was employed to collect strains with ACC deaminase activity.The strains were subsequently isolated and purified using common media such as NB and LB,and finally induced and screened using specific media such as PAF,DF,and ADF.The strains exhibiting ACC deaminase activity were subjected to enzyme activity determination,physiological and biochemical experiments,and antibacterial and antioxidant activity experiments.Secondly,lavender seedlings were grown in sand and then water-cultured to collect the exudate solution.The solution was filtered using a 0.45μm filter membrane,and the exudate solid was collected using vacuum rotary evaporation and freeze-drying methods and subsequently identified.Thirdly,the effects of bacterial strains and exudate solutions on the morphological data of wheat seeds and seedlings were analyzed using IBM SPSS version 25.0.[Results] Firstly,five strains with ACC deaminase activity were isolated,including Pseudomonas rhizophila,Pseudomonas savastanoi,Klebsiella pasteurii,Klebsiella pneumoniae,and Serratia plymuthica.The ACC deaminase activities were 0.546U/mg,0.487 U/mg,0.277 U/mg,0.312 U/mg,and 0.081 U/mg,respectively.Pseudomonas rhizophila had the highest ACC deaminase activity,while Serratia plymuthica had the lowest.Antibacterial and antioxidant activities of the first four strains is statistically significant.Pseudomonas rhizophila,Pseudomonas savastanoi,Klebsiella pasteurii,and Klebsiella pneumoniae also demonstrated statistically significant antibacterial and antioxidant activities.Secondly,306 different types of chemical components were identified in the lavender root exudates,which were primarily divided into nine categories,including acid,alcohol,sugar,amino acid,amine,purine and pyrimidine,ester,ketone,and phenol.The contents of acid,alcohol,sugar,and amino acid were relatively high,accounting for 35.61%,29.07%,14.91%,and 4.51%,respectively.The relative content of amine was 1.02%,while the relative content of purine and pyrimidine,ester,ketone,and phenol were low,ranging from0.13% to 0.68%.This indicates that the components of lavender root exudates are abundant and complex,with significant differences in content,and that acid,alcohol,sugar,and amino acid are the main components.Finally,through growth-promoting experiments on wheat seeds and seedlings,it was found that the first four strains,Pseudomonas rhizophila,Pseudomonas savastanoi,Klebsiella pasteurii,and Klebsiella pneumoniae,exhibited a certain degree of growth-promoting effect at different stages of wheat growth,while Serratia plymuthica showed a certain degree of inhibition.[Conclusion] Through experiments,we found that 4 kinds of rhizosphere ACC deaminase bacteria can effectively promote the growth of plants under the action of root exudates.In the comparative experiment,the plant growth of the treatment group added with the bacteria was significantly better than that of the control group without the bacteria added.In summary,the rhizosphere ACC deaminase bacteria is a potential plant growth-promoting bacteria,which can be used as a new type of biofertilizer in plant growth,and has certain feasibility and application prospects.These findings provide new ideas and new directions for the development of biological fertilizers,which have important scientific significance and application value.