The impact of endogenous and exogenous fungi in saline-alkali soil on the growth and root system of pine trees

The objective is to explore planting methods that enhance the ability of black pine to cope with salt stress environments, improve its growth under such conditions, and observe its growth and physiological characteristics under various experimental conditions. For this purpose, endophytic mycorrhizal Indian pear-shaped fungus and ectomycorrhizal two-colored wax mushrooms were selected and inoculated onto potted black pine seedlings, and a control group was set up. After inoculation, the mycorrhizal infection rate, salt damage symptoms, growth rate, root parameters, and various physiological indicators under different salt stress durations were evaluated. Results showed that as the salt concentration was raised to 6.0 g/L, the infection rates of endophytic and ectomycorrhizal fungi decreased from 55.8% to 17.4% and 51.9% to 15.3%, respectively. Plants with ectomycorrhizal fungi had stronger mycorrhizal dependence. Inoculating mycorrhizal fungi can increase plant height, reduce salt damage, and significantly increase plant biomass (p < 0.05). At 3.0 g/L, the biomass accumulation of the mycorrhizal group reached its peak. Mycorrhizal fungi were generally beneficial for plant roots in analyzing root morphology and parameter indicators. Significant differences existed in root length, volume, and diameter compared to the control group (p < 0.05). The quantity of branches and fractal dimensions showed excellent performance. In addition, mycorrhizal fungi were beneficial for the accumulation of osmoregulatory substances and antioxidant enzyme activity in plants, reducing the content of malondialdehyde. In conclusion, there were differences between the experimental and control groups in terms of plant growth, physiological indices, and root system, with the mycorrhizal-inoculated group having a better ability to cope with salt stress.