ABSTRACT
This study aimed to investigate the mechanisms by which dark septate endophytes (DSE) regulate salt tolerance and the accumulation of bioactive constituents in licorice. First, the salt stress tolerance and resynthesis with the plant effect of isolated DSE from wild licorice were tested. Second, the performance of licorice inoculated with DSE, which had the best salt-tolerant and growth-promoting effects, was examined under salt stress. All isolated DSE showed salt tolerance and promoted plant growth, withCurvularia lunata D43 being the most effective. Under salt stress, C. lunata D43 could promote growth, increase antioxidant enzyme activities, enhance glycyrrhizic acid accumulation, improve key enzyme activities in the glycyrrhizic acid synthesis pathway, and induce the expression of the key enzyme gene and salt tolerance gene of licorice. The structural equation model demonstrated that DSE alleviate the negative effects of salt stress through direct and indirect pathways. Variations in key enzyme activities, gene expression, and bioactive constituent concentration can be attributed to the effects of DSE. These results contribute to revealing the value of DSE for cultivating medicinal plants in saline soils.
Subject(s)
Endophytes , Glycyrrhiza , Glycyrrhizic Acid , Salt Stress , Glycyrrhizic Acid/metabolism , Glycyrrhiza/chemistry , Glycyrrhiza/metabolism , Glycyrrhiza/microbiology , Endophytes/metabolism , Endophytes/genetics , Salt Tolerance , Ascomycota/metabolism , Ascomycota/growth & development , Plant Proteins/metabolism , Plant Proteins/genetics , Gene Expression Regulation, PlantABSTRACT
Under different pH conditions, the hydrothermal and co-precipitation method was used to synthesize layered double hydroxides (LDHs) coated on bio-ceramic substrates with three different Zn2+/Al3+ molar ratios. Applying the original and six kinds of modified bio-ceramic substrates coated with ZnAl-LDHs (bio-ceramic/ZnAl-LDHs) in simulated vertical-flow constructed wetlands, experiments for phosphorus removal and isothermal adsorption were conducted to analyze the mechanism and effect of each synthesis factor. The results showed that ZnAl-LDHs (pH=11) had a more obvious effect on phosphorus removal, especially for bio-ceramic/ZnAl-LDHs (pH=11, 1:1), whose average removal rates of TP, TDP and SRP were enhanced over 70%. Its maximum adsorption capacity for phosphorus was three times higher than that of the original bio-ceramic. Both pH and Zn2+/Al3+ molar ratio affected the configuration and coating properties of bio-ceramic/ZnAl-LDHs at the time of synthesis, and pH was the main synthesis factor for phosphorus removal efficiency of bio-ceramic/ZnAl-LDHs. Through reasonable regulation of pH and Zn2+/Al3+ molar ratio when bio-ceramic/ZnAl-LDHs was synthesized, the phosphorus removal efficiency could be improved effectively.
