Abstract:

Objective: This study investigated the effects of the interaction between Bacillus paramycoides JYZ-SD5 and Schizophyllum commune Be on the growth and salt tolerance of Metasequoia glyptostroboides under salt stress, in order to explore the mechanism of action, and to provide a reference for the use of beneficial microorganisms to improve the salt tolerance of woody plants and the bioremediation of saline-alkali land. Method: A pot experiment was conducted to investigate the effects of B.paramycoides JYZ-SD5 and S.commune Be on the physiological and metabolic indexes and salt tolerance of M.glyptostroboides under NaCl stress. Result: 1) Compared with control seedlings, the biomass and root growth parameters of M.glyptostroboides were improved by different inoculation treatments, and the effect of co-inoculation with JYZ-SD5+Be was better than single inoculation with JYZ-SD5 or Be.The height growth, diameter growth, root length, root surface area, root volume, root tips number and branches of M.glyptostroboides of co-inoculation with JYZ-SD5+Be were significantly increased by 65.47%, 63.46%, and 1.05, 1.51, 2.2, 1.88, and 2.31 times, respectively (P < 0.05).2) Under salt stress, compared with uninoculated control, all inoculation treatments effectively alleviated the damage of salt stress on M.glyptostroboides leaves and relieved the symptoms of salt damage.Single inoculation with JYZ-SD5 improved the soluble sugar, soluble protein and proline significantly by 12.4%, 62.58%, and 38.99%, respectively (P < 0.05), single inoculation with Be and co-inoculation with JYZ-SD5+Be significantly improved proline by 122% and 35.64%(P < 0.05).3) Under salt stress, compared with uninoculated control, all inoculation treatments effectively reduced the H₂O₂ content, O₂^·-generation rate, MDA content and electrolyte leakage, among which, single inoculation with JYZ-SD5 significantly reduced by 26.58%, 9%, 15.85%, and 18.76%(P < 0.05), single inoculation with Be reduced by 8.91%, 7.77%, 8.54%, and 22.09%, co-inoculation with JYZ-SD5+Be significantly reduced by 15.58%, 26.38%, 53.66% and 30.39%(P < 0.05), respectively.At the same time, all inoculation treatments significantly reduced the activity of SOD, POD, CAT, APX and GR.4) Under salt stress, compared with uninoculated control, all inoculation treatments improved K⁺ content and reduced Na⁺ content, and thus reduced Na⁺/K⁺ ratio which was the highest in the single inoculation with Be and was significantly reduced by 23.84% and 26.58% in shoots and leaves of M.glyptostroboides (P < 0.05), respectively. Conclusion: This study showed that B.paramycoides JYZ-SD5 and S.commune Be can promote the growth of M.glyptostroboides, alleviate the damage of salt stress on M.glyptostroboides and improve the tolerance of M.glyptostroboides to salt stress by raising the plant water absorption and accumulation of osmotic regulation substances, maintaining the cell membrane stability, reducing the level of membrane lipid peroxidation and the accumulation of reactive oxygen species and antioxidant enzymes activity and reducing the Na⁺/K⁺ ratios.

Key words: Bacillus paramycoides JYZ-SD5, Schizophyllum commune Be, Metasequoia glyptostroboides, Salt stress, Salt tolerance