Effects of Piriformospora indica fungi symbiotic on the quantity of essential oil and some physiological parameters of peppermint in saline conditions

In order to evaluate the effect of Piriformospora indica fungi inoculation on some physiological parameters of peppermint medicinal plant under salt stresses, a field experiment was arranged in a factorial experiment based on completely randomized design with three replications. Treatments including P.indica symbiosis and four salinity levels (irrigation with distilled water and the Caspian Sea water mixture at of 0, 3, 6 and 9 dS m-1). The measured parameters were leaf dry weight, leaf total phenolics, flavonoids, anthocyanins, radical scavenging, essential oil yield and the content of Na, P and K and stomatal conductance. Results showed that with increasing of salinity, the anthocyanins, flavonoids and Na content were increased, while P and K content, leaf dry weight and essential oil yield were decreased. The symbiotic fungi increased anthocyanins and flavonoids content by 17 and 31%, respectively as compared to the uninoculated control plants. Fungal treatment, reduced the negative effects of salinity on stomatal conductance, P and K content, leaf dry weight, essential oil yield and also decreased Na content in saline conditions. In 9 dS m-1 of salinity, fungi inoculation could increase total phenol content and essential oil yield up to 37 and 76%, respectively. It seems, the root inoculation of the peppermint medicinal plants with P. indica, stimulates the synthesis of phenolic compounds and essential oils, also increases the nutrient uptake which ameliorate the negative effects of salinity in the plant.