Abstract
High salinity levels pose a significant challenge to agricultural productivity, as it impairs photosynthesis, water and nutrient uptake, and cellular homeostasis in plants. Arbuscular mycorrhizal fungi (AMF) are symbiotic microorganisms that can improve plant tolerance to salinity, but their effects on plant photosynthetic efficiency, especially of Photosystem II, are poorly understood. This study examined the impact of AMF inoculation on the growth, physiology, and biochemistry of pistachio plants exposed to salt stress in a greenhouse experiment. The experimental findings demonstrated that that AMF symbiosis increased the growth and the K, Ca, Mg, P, K/Na, and Ca/Na ratios, and reduced the Na and Cl concentrations, of pistachio plants under salinity. AMF inoculation also decreased the electrolyte leakage, malondialdehyde, and hydrogen peroxide levels, and increased the relative water content, water use efficiency, glycine betaine, soluble sugars, alpha-tocopherol, and carotenoids of pistachio plants under salinity. Furthermore, AMF inoculation mitigated the salinity-induced reduction in chlorophyll content, maximum quantum efficiency of Photosystem II (Fv/Fm), effective quantum efficiency of Photosystem II (Fv’/Fm’), and photochemical quenching (qP), and the salinity-induced increase in non-photochemical quenching (NPQ) and chlorophyll a/b ratio. Additionally, AMF inoculation improved the net photosynthesis rate, stomatal conductance, and transpiration rate, and reduced the intercellular CO2 concentration, of pistachio plants under salinity. These findings indicate that AMF inoculation enhances the photosynthetic capacity, water relations, and ion homeostasis of pistachio plants, and confers salinity tolerance and improved growth and performance.