Piriformospora indica improves salinity stress tolerance in Zea mays L. plants by regulating Na⁺ and K⁺ loading in root and allocating K⁺ in shoot

Piriformospora indica is known as a fungus that can easily colonize a wide range of plants and enhance host’s growth and tolerance to abiotic stresses, including salinity. The mechanistic basis behind this phenomenon remains poorly understood. This work was aimed to fill in this gap and reveal mechanisms enhancing salinity tolerance in maize roots colonised by P. indica. A range of agronomic and physiological characteristics were compared between inoculated and non-inoculated maize plants under 0/100/200 mM NaCl conditions. The impact of P. indica inoculation or root’s cytosolic K+ retention ability were also assessed using micro-electrode ion flux estimation technique. The results showed that inoculated plants had higher biomass, higher stomatal conductance, lower K+ efflux from roots and higher potassium content in shoots than non-inoculated plants under salt stress. Collectively, the results indicated that the beneficial effects of inoculation on plant performance under saline conditions were mainly attributed to the improved stomata operation associated with higher rate of K delivery into the shoots.