Piriformospora indica inoculation alleviates the adverse effect of NaCl stress on growth, gas exchange and chlorophyll fluorescence in tomato (Solanum lycopersicum L.)

Salinity is now an increasingly serious environmental issue that affects the growth and yield of many plants. In the present work, the influence of inoculation with the symbiotic fungus, Piriformospora indica, on gas exchange, water potential, osmolyte content, Na/K ratio and chlorophyll fluorescence of tomato plants under three salinity levels (0, 50, 100 and 150mm NaCl) and three time periods (5, 10 and 15days after exposure to salt) was investigated. Results indicate that P.indica inoculation improved growth parameters of tomato under salinity stress. This symbiotic fungus significantly increased photosynthetic pigment content under salinity, and more proline and glycine betaine accumulated in inoculated roots than in non-inoculated roots. P.indica further significantly improved K+ content and reduced Na+ level under salinity treatment. After inoculation with the endophytic fungus, leaf physiological parameters, such as water potential, net photosynthesis, stomatal conductance and transpiration, were all higher under the salt concentrations and durations compared with controls without P.indica. With increasing salt level and salt treatment duration, values of F-0 and qP increased but F-m, F-v/F-m, F-v/F-m and NPQ declined in the controls, while inoculation with P.indica improved these values. The results indicate that the negative effects of NaCl on tomato plants were alleviated after P.indica inoculation, probably by improving physiological parameters such as water status and photosynthesis.