以不同浓度的灰色链霉菌发酵液处理干旱胁迫的桔梗根际土壤为研究对象,将不同浓度的灰色链霉菌发酵液(原液,原液稀释10倍,原液稀释50倍,原液稀释100倍(菌数1×108cfu·mL-1),原液稀释150倍)200 mL分别与花盆0~20 cm的土搅拌,无菌水作为对照(CK),土壤的持水量控制在45% 左右,待桔梗生长至四叶期时,分别于7、14、21、28、35 d取其根际土壤(0~20 cm).采用比色法和高锰酸钾滴定法测定桔梗根际土壤蔗糖酶、脲酶、过氧化氢酶、纤维素酶和蛋白酶活性的变化,稀释平板计数法测定微生物数量.结果表明,随着灰色链霉菌发酵液稀释倍数增加,桔梗根际土壤蔗糖酶、脲酶、过氧化氢酶、纤维素酶和蛋白酶活性均逐渐升高,发酵液稀释到100倍时,土壤蔗糖酶、脲酶、过氧化氢酶、纤维素酶和蛋白酶活性均达到峰值,比CK的峰值分别提高了68%、12.63%、11.53%、128.24%、43.51%.在第35天时,用灰色链霉菌发酵液稀释100倍处理干旱胁迫的桔梗根际土壤有机质、全氮、有效磷、速效钾含量比CK分别升高了280.13%、99.15%、60% 和60.12%;灰色链霉菌发酵液处理的土壤中细菌不断增加,在第35天时比CK增加了355.43%,而土壤中放线菌和真菌先增加后降低,但高于CK.土壤酶活性、土壤养分因子和土壤微生物数量的相关性分析表明,脲酶与有机质、全氮、有效磷、速效钾和细菌呈极显著正相关(P<0.01),纤维素酶与有机质、全氮、有效磷、速效钾、细菌和放线菌呈极显著或显著正相关,蛋白酶与有效磷、速效钾、细菌、放线菌和真菌呈极显著或显著正相关,蔗糖酶和过氧化物酶与有机质、全氮、有效磷、速效钾和细菌呈负相关且不显著,与放线菌、真菌正相关且不显著.%Platycodon grandiflorum of rhizosphere soil under drought stress was treated with different concentrations of Streptomyces griseus fermentation medium and different concentrations of Streptomyces griseus fermentation broth(origi-nal solution,and original solution diluted 10,50,100 times(The number of bacteria was 1×108cfu·mL-1)and 150 times),mixed with 0~20 cm of the soils in 200 mL pots respectively,sterile water was as control(CK).Soil water holding capacity was controlled around 45%.When the Platycodon grandiflorum growth reached four leaves,the rhizo-sphere soil(0~20 cm)was taken at 7,14,21,28,and 35 days.The changes of rhizosphere soil invertase,urease, catalase,cellulase and protease activities were measured with colorimetry and potassium permanganate titration,and the number of microbes were determined by dilution method of plate counting.The results showed that the activity of inver-tase,urease,catalase,cellulase and protease in the rhizosphere soil of Platycodon grandiflorum increased with the in-crease of the dilution of the fermentation broth of Streptomyces griseus.When the fermented broth was diluted to 100 times,peak of invertase,urease,catalase,cellulase and protease activities reached 68%,12.63%,11.53%, 128.24%,43.51% respectively higher than that of CK.Platycodon grandiflorum rhizosphere soil treated by Strepto-myces griseus fermentation broth diluted 100 times,significantly improved soil organic matter,total nitrogen,available P, available K contents by 280.13%,99.15%,60%,60.12% respectively higher than CK at 35 d.The bacteria in soil treated by Streptomyces griseus fermentation broth continuously increased,in by 355.43% than CK at 35 d.Actinomyces and fungi in the soil increased first and then decreased,but were all higher than CK.Correlation analysis of soil enzyme activities,soil nutrient factors and soil microorganisms showed that urease and organic matter,total N,available P, available K,bacteria were significantly positive correlated(P<0.01).Cellulase and organic matter,total N,available P,available K,bacteria,actinomycetes were extremely significant or significantly positive correlated.Protease and effec-tive phosphorus,rapidly-available potassium,bacteria,actinomyces,fungi were extremely significant or significant posi-tive correlated.Invertase,peroxidase(pod)and organic matter,total N,available P,available K,bacteria were not significant and negative correlated,but invertase,peroxidase and actinomyces,fungi had a positive correlation but not significant.
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