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    促生肠杆菌和假单胞菌接种对干旱胁迫下苜蓿幼苗根系微环境的影响

    Effects of Enterobacter sp. and Pseudomonas sp. inoculation on root microenvironment of alfalfa seedlings under drought stress

      摘要
    • 摘要:
      目的 从土壤微生态角度，探究促生菌株增强植物抗旱性、促进植物生长的作用机制。
      方法 以具备多重抗逆与促生特性的肠杆菌（D1）和假单胞菌（D2）为供试菌株，通过苜蓿盆栽试验，设置单一菌剂（D1、D2）和复合菌剂（F）接种处理，分析干旱条件下不同接种处理对苜蓿根际土壤理化性质、酶活性以及根系细菌多样性和群落结构的影响。
      结果 （1）与未接种对照（CK）相比，接种处理显著增加了苜蓿幼苗生物量，显著降低了根际土壤pH值和电导率，显著提高了土壤含水量和有效磷含量（P < 0.05）。显著提升了土壤关键酶活性：与CK相较，D1、D2和F处理组土壤碱性磷酸酶活性分别提高了92.26%、141.67%和72.02%，脱氢酶活性分别提高了116.93%、201.63%和110.12%，蔗糖酶活性分别提高了52.54%、42.80%和34.43%，脲酶活性分别提高了54.66%、33.27%和121.67%。（2）复合菌剂（F）显著改变了苜蓿根际土壤和根部内生细菌的多样性和群落结构，提高了根系细菌群落的丰富度和多样性，并促进绿弯菌门、节杆菌属和肠杆菌属等在根际土壤中富集，以及拟杆菌门、新鞘氨醇菌属和肠杆菌属等在根内的富集。（3）土壤理化因子关联分析表明，土壤含水量、有效钾及有效磷是驱动苜蓿根系细菌群落的主要环境因子。
      结论 在干旱条件下，接种促生菌可通过改良土壤的保水性、促进养分转化、调节根系微生物群落组成来优化根际土壤微环境，从而缓解干旱对植物的损伤并促进植物生长，且复合菌剂的效果优于单一菌剂，具备良好的开发与应用潜力。

       

      Abstract:
      Objective The purpose of this study was to explore the mechanism of plant growth promoting rhizobacteria (PGPR) promoting plant growth and enhancing plant drought resistance from the perspective of soil microecology.
      Method Enterobacter sp. (D1) and Pseudomonas sp. (D2) with multiple stress resistance and growth promoting potential were selected as test strains, the effects of single inoculant D1, D2 and compound inoculant F on the physical and chemical properties, enzyme activities of alfalfa rhizosphere soil, rhizobacteria and endophytes diversity and community structure under drought stress were analyzed through alfalfa pot experiment.
      Result (1) Compared with control, alfalfa seedling biomass in the inoculated group increased significantly, pH and conductivity of rhizosphere soil decreased significantly, and the soil water content and available phosphorus content increased significantly (P < 0.05). Soil alkaline phosphatase activities of group D1, D2 and F were significantly increased by 92.26%, 141.67%, and 72.02%, dehydrogenase activities were significantly increased by 116.93%, 201.63% and 110.12%, sucrase activities were significantly increased by 52.54%, 42.80% and 34.43%, urease activities were increased by 54.66%, 33.27% and 121.67%, respectively. (2) Compound inoculant F could significantly alter the bacterial diversity and community structure of alfalfa root system, increase the richness and diversity of rhizospheric and endophytic bacterial communities, and promote the enrichment of Chloroflexia, Arthrobacter and Enterobacter in rhizosphere soil, and enrich Bacteroidetes, Sphingomonas and Enterobacter in the roots. (3) The correlation analysis between soil physicochemical factors and bacterial communities showed that soil water content, available potassium and available phosphorus were main factors affecting the bacterial community of alfalfa roots.
      Conclusion Under drought conditions, plant growth promoting rhizobacteria (PGPR) could alleviate the damage of drought to plants and promote plant growth by promoting soil water retention and nutrient transformation, regulating the community composition of root microorganisms, improving rhizosphere soil microenvironment. The effect of compound inoculant(F) is better than that of single inoculant, which has the potential of further development and utilization.

       

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