| The suitable p H for tea tree is 4.5 ~ 6.0.When the p H of tea garden soil is below 4.0,tea tree growth is restrained.The soil p H of current tea garden is constantly decreased due to various reasons,which has become urgent problem of the world tea garden management.Tea is an Al-accumulating plant.Soil with a proper concentration of Al can promote the growth of tea tree,particularly promotion of lateral root formation.The most suitable concentration of exchangeable Al in the high-yield tea garden is usually 3 ~ 5 cmol/kg.At present,the soils in the tea garden become more acid,which result in an increasing of active Al in the soil.This can seriously influence the growth of tea tree.The aim of this study is based on the analysis of the tea garden soil microorganisms to find out several acid-resist microorganisms,and furtherly reveal its acid-resistent mechanism.We want to find a method that can improve tea garden soil and other acid soil of agriculture and forestry by acid-resistent microbes.(1)Effects of fertilization on soil and soil microorganisms.Soil p H in tea garden reached the maximum in 5 days after urea application and then showed obvious decreasing trend.After 40 days,the soil p H was significantly lower in three treated tea gardens than in the control.The soil microbial biomass carbon in the tea garden and abandoned-land reached maximum in 5 days after the urea application,and then obviously decreased with time,while changed little from 35 to 45 days.The base respiration of the tested soil increased to the maximum in 5 days after fertilization,and then decreases rapidly.After 15 days of fertilization,no significant difference of base respiration was found between the treatment and control.The soil enzyme activity reached maximum in 5 days after treatment,and then decreased evidently.Sucrase,protease and acid phosphatase activities decreased faster from 5 to 35 days,became stable from 35 to 45 days,which were still higher than the control.The result indicates that urea fertilization has a long-term effect on the activities of sucrase,protease and acid phosphatase.(2)Effects of lime treatment on soil and soil microorganisms.The soil p H became obviously higher on abandoned-land than on tea garden after Cal and Ca2 treatments,while the result was opposite under Ca3 treatment.The tea garden soil average well color development(AWCD)gradually increased with the increase of lime dosage.Compared with the control,lime treatments caused the highest increase rate in AWCD in 144 h in 8-,50-and 90-year-old tea garden.The effects of lime treatments on microbial function diversity index were similar to that on AWCD.Soil microbial functional diversity index increased significantly with the increase of lime dosage.Compared with controls,the Ca3 treatment has significant impact with increasing rates ranked as 80-year-old tea garden > 8-year-old tea garden and 50-year-old tea garden.(3)Screening of acid-resistent microorganisms and its mechenisms.From tea garden soil,we screened the bacteria(QM6)that can grow normally in the acid conditions and can improve acid soil.We isolated individuals with cultivation for further research.We identified this bacterial strain as Burkholderia through morphologic observation and 16 s r RNA sequence homology analysis.This bacteria can grow normally in acid soil with p H 3.5 and increase soil p H to 8.To reveal its acid-resistent mechanism,we tried Amino acid metabolic method and protein detection method,and found a great excess expression of fatty acid metabolism enzyme in acid condition.The results indicate that the acid-resistent mechanism of this bacteria strain could be connected to fatty acid metabolism. |
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