Effect of Endophytic fungus Serendipita indica on some growth characteristics and secondary metabolites of Mentha piperita under lead toxicity in soil

Root endophytic fungi are beneficial soil microorganisms that affect the growth and production of secondary metabolites by causing physiological changes in their host plants. In this study, the effects of Serendipita indica (four levels of fungus including without fungus treatment, and 1, 2 and 3 pieces of fungus solid medium with dimensions of 0.2×1×1 cm) on root colonization, growth parameters, photosynthetic pigments as well as the quantity and quality of peppermint essential oil were evaluated under without stress condition and lead stress (800 mg/kg soil). The results showed that lead reduced the percentage of colonization, growth parameters, the amount of pigmentation and the essential oil quantity. The use of endophyte fungus had positive effects on the parameters studied. By increasing the amount of fungus in the soil, the percentage of colonization, fresh and dry weight of root and shoot, the concentration of photosynthetic pigments were significantly increased. The results of the GC-MS showed 27 phytochemical compounds, which the most essential oil compounds in the different treatments were menthol (38.01-48.90%), (10.68-17.54%), menthone (4.8-8.84%) and neomenthol (4.17-7.87%). Maximum menthol and p-menth-1-9-ol contents was obtained using S. indica (3 pieces of fungus solid medium) without lead treatment. Using these results, it can be said that S. indica has increased growth indicators and photosynthetic pigments, as well as changes in peppermint essential oil, and significantly reduced the harmful effects of lead in medicinal plant peppermint.