盐胁迫环境下接种根际促生细菌对白蜡树根际生物学特征及其生长的影响

目的]探讨不同盐胁迫生境中接种根际促生细菌(PGPR)对白蜡树根际的作用效果,为明确PGPR对白蜡树耐盐性的改善效果以及盐胁迫环境下PGPR的推广应用提供理论依据。方法]通过盆栽试验,研究不同盐胁迫(轻度、中度、重度)及其接种阴沟肠杆菌(PGPR)对白蜡树根际生物学特征与生长的影响。结果]盐胁迫显著降低了白蜡树根际微生物数量、微生物量碳、氮含量和脲酶、多酚氧化酶、过氧化氢酶、蔗糖酶活性,且其降幅随盐胁迫梯度的增加而增大;当接种PGPR后,白蜡树根际微生物数量、微生物量碳、氮含量和脲酶、多酚氧化酶、过氧化氢酶、蔗糖酶活性均呈上升趋势,其中轻度盐胁迫接种PGPR处理的细菌数、放线菌数和微生物总量达最高,分别较对照显著提高14.64%,24.01%和17.04%,而脲酶、多酚氧化酶、蔗糖酶活性与对照差异不显著,但显著高于其他处理。同时,白蜡树的根体积、根系总吸收面积与活跃吸收面积随着盐胁迫程度的加剧呈递减趋势,但接种PGPR后,对应的根系指标均有增加,其中轻度盐胁迫接种PGPR处理的活跃吸收面积显著高于对照15.97%。此外,同对照相比,不同程度盐胁迫均显著降低了白蜡树的地径、株高,而接种PGPR却显著提高了地径、株高,其中轻度盐胁迫接种PGPR处理的地径、株高与对照差异不显著,但显著高于其他处理。结论]轻度盐胁迫下(盐分含量0.2%)接种阴沟肠杆菌能显著改善白蜡树根际生物学特征,并促进白蜡树生长,其作用效果显著优于中度、重度盐胁迫下接种阴沟肠杆菌。

Effects of Inoculating Plant Growth-Promoting Rhizobacteria on Biological Characteristics of Rhizosphere and Growth of Fraxinus Chinensis Under Salt Stress

Objective] The paper aims to explore the effect of inoculating plant growth-promoting rhizobacteria (PGPR) on the rhizosphere soil of Fraxinus chinensis under different salt stress conditions, and to clarify the improving effect of PGPR on salinity tolerance of F. chinensis and provide theoretical support for the extension of PGPR in salt stress environment.Methods] We used a pot experiment covering different salt stresseslight salt stress(LS), moderate salt stress(MS), and severe salt stress(SS)] and corresponding inoculating PGPR to evaluate the effects of different treatments on the biological characteristics of rhizosphere soil and growth of F. chinensis.Results] The microorganism population, the contents of microbial biomass carbon and microbial biomass nitrogen, the activities of urease enzyme, polyphonic oxidase enzyme, catalase enzyme and invertase enzyme under salt stress conditions were significantly decreased, and the decreased magnitude become larger and larger along with the increasing salt stress, whereas the corresponding indexes showed an increasing trend after inoculating PGPR. The populations of bacteria, actinomycetes and total microbial by LS+P treatment achieved the maximum value, increased by 14.64%, 24.01% and 17.04% compared with CK, respectively, and the activities of urease enzyme, polyphonic oxidase enzyme and invertase enzyme had no significant differences between LS+P and CK treatments, while they significantly increased compared with the other treatments. Meanwhile, the root volume, total absorption area and active absorption area also demonstrated a trend of decreasing as the degree of salt stress increased, but the corresponding indexes increased after inoculating PGPR. The active absorption area in LS+P treatment markedly increased by 15.97% in comparison with CK. Additionally, compared to CK, the ground diameter and plant height significantly decreased in the treatments of different degrees of salt stress, while an opposite trend was presented after inoculating PGPR. And the ground diameter and plant height in LS+P treatment had no significant differences compared with CK, whereas they significantly increased compared with the other treatments.Conclusion] The inoculating PGPR under light salt stress could significantly improve the biological characteristics of rhizosphere soil and growth of F. chinensis, and the effect was significantly higher than inoculating PGPR under moderate and severe salt stress.