醋酸钙不动杆菌对盐碱胁迫下达乌里胡枝子促生效应研究

Acinetobacter calcoaceticus promotes the seedling growth of Lespedeza daurica under saline-alkaline stress

摘要:

达乌里胡枝子(Lespedeza davurica)是黄土高原地区重要的生态修复草种，但土壤盐碱化极大影响了达乌里胡枝子的生长，制约了其经济和生态价值。接种根际促生菌剂是提高植物对盐碱胁迫抗性的重要途径。【目的】验证醋酸钙不动杆菌(Acinetobacter calcoaceticus)对盐碱胁迫下达乌里胡枝子幼苗和成株的促生效应，初步揭示其促进豆科植物生长的潜在机理，为田间应用提供理论依据。【方法】采用解钾培养基对2株达乌里胡枝子根际分离的醋酸钙不动杆菌的解钾能力进行测定；采用液体发酵法对菌株分泌铁载体、吲哚乙酸(indole-3-acetic acid, IAA)的能力进行定量测定；分别在培养皿和盆栽条件下，验证菌株的促生能力及其机制。【结果】菌株DP25和DP27具有解钾和分泌铁载体、IAA的能力，其中相对铁载体表达量值(siderophore, SU)分别为53.13%和86.67%，IAA含量分别为1.01 mg/L和17.31 mg/L；菌株DP25显著提高了培养皿中达乌里胡枝子幼苗的茎长和根长；菌株DP25和DP27对盐碱胁迫下达乌里胡枝子成株的光合色素合成及其光合作用产生积极影响；菌株DP25和DP27显著提高了盆栽条件下达乌里胡枝子成株的株高、茎粗、根表面积、总根长、分叉数；菌株DP27还显著提高了地上和地下生物量、根体积、总根尖数、根系活力。【结论】接种醋酸钙不动杆菌对达乌里胡枝子幼苗和成株均表现出良好的促生作用，其中分泌IAA是促进幼苗生长的主要因素，而提高光合能力和根系形态建成在促进成株生长中发挥关键作用。醋酸钙不动杆菌可用于开发黄土高原盐碱地区建植达乌里胡枝子的促生菌剂。

Abstract:

Lespedeza davurica is a grass for ecological restoration in the Loess Plateau. The saline-alkaline soil in the Loess Plateau greatly affects the growth and restricted the economic and ecological values of L. davurica. Inoculation of growth-promoting rhizobacteria is an important way to improve plant tolerance to saline-alkaline stress. [Objective] This study aims to reveal the effect and mechanism of Acinetobacter calcoaceticus in promoting the seedling growth of L. davurica under saline-alkaline stress, preliminarily disclose the potential growth-promoting mechanism of legumes, and provide a theoretical basis for the field application of this bacterium. [Methods] The potassium-containing medium was used to measure the potassium-solubilizing ability of two A. calcoaceticus strains isolated from L. davurica rhizosphere. The liquid fermentation method was employed to determine the production of siderophore and indole-3-acetic acid (IAA) by the two strains. Furthermore, we carried out petri dish and pot experiments to determine the growth-promoting effects of A. calcoaceticus on L. davurica seedlings under saline-alkaline stress. [Results] Strains DP25 and DP27 had the abilities to solubilize potassium and showed the siderophore production of 53.13% and 86.67% and the IAA production of 1.01 mg/L and 17.31 mg/L, respectively. Compared with the control, the inoculation of DP25 significantly improved the stem length and root length of L. davurica seedlings in petri dishes. The pot experiments showed that strains DP25 and DP27 had positive effects on the photosynthetic pigment synthesis and photosynthesis of the plants under saline-alkaline stress. Compared with the control, the inoculation with strains DP25 and DP27 increased the plant height, stem diameter, root surface area, total root length, and bifurcation number of L. davurica plants in pots. In addition, strain DP27 increased the aboveground biomass, underground biomass, root volume, total root tips, and root activity. [Conclusion] A. calcoaceticus demonstrates growth-promoting effect on the seedlings and adults of L. davurica. It secretes IAA to promote the growth of seedlings and improves the photosynthetic capacity and root morphogenesis to facilitate the growth of the adults under saline-alkaline stress. A. calcoaceticus can be used as a growth-promoting bacterium for planting L. daurica in the saline-alkaline area of Loess Plateau.