Mycorrhization of Quercus dentata seedlings with Laccaria bicolor enhances salt tolerance of plants only under relatively moderate soil salinity level

Background Soil salinization is a growing global concern in many ecosystems. Although ectomycorrhizal fungi have been shown to alleviate the effects of salinity in some tree species, uncertainties persist concerning their effectiveness when plants are exposed to different salinity levels that are commonly present in salt-affected soils. Objective This study explored the effects of Laccaria bicolor on Quercus dentata seedlings under different levels of salt stress. Methods Q. dentata seedlings were grown in pots and were either non-inoculated (mycorrhizal control) or inoculated with the ectomycorrhizal fungus L. bicolor . The seedlings were then treated with three NaCl concentrations (0, 0.4%, and 0.8%), that was added to the soil for 30 days, after which plant physiological, stoichiometric, and growth characteristics were examined. Results NaCl exposure significantly impaired growth and physiological parameters in all seedling groups. The influence of L. bicolor on Q. dentata seedlings varied with salt concentration. Under moderate salinity, the seedlings colonized by L. bicolor exhibited an enhancement in root biomass and leaf chlorophyll concentrations, concomitant with a reduction in leaf Na ⁺ concentrations and the Na ⁺ /K ⁺ ratios. Conversely, under relatively high salinity, colonization of L. bicolor was associated with a reduction in leaf water content and fluorescence parameters, as well as an elevation in leaf Na ⁺ concentrations. Conclusions The effect of ectomycorrhizal fungus L. bicolor on Q. dentata seedlings was dependent on NaCl concentration, and our results indicate that the use of L. bicolor in afforestation efforts with Q. dentata would only be effective under relatively low soil salinity levels.