Piriformospora indica SYMBIOSIS AND IRON OXIDE NANOPARTICLES ALLEVIATES DROUGHT STRESS IN SOYBEAN PLANTS THROUGH IMPROVED ON PHOTOSYNTHETIC GAS EXCHANGE AND SUCROSE PHOSPHATE SYNTHASE AND ACID PHOSPHATASE

Drought stress is one of the most destructive environmental stresses which affect the performance of soybean photosynthetic apparatus and can reduce plant productivity. This study aimed to evaluate the effects of iron oxide nanoparticles (NPs), Piriformospora indica and drought effects on gas exchange, sucrose phosphate synthase (SPS) and acid phosphatase (ASP) activities. Treatments included inoculation and non-inoculation of P. indica, NPs (0, 0.5 and 0.75 gL-1) and three irrigation regimes (control, irrigation after 50% and 75% depleting of soil water content). This study showed that drought stress reduced SPAD values and increased membrane electrolyte leakage. It also had negative effect on photosynthetic functional parameters. Nevertheless, inoculation of soybean with P. indica can provide drought-tolerance by improving the net photosynthesis, carboxylation efficiency, P, SPS and ASP parameters, keeping membrane stability and raising chlorophyll content. In addition, similar to P. indica, NPs treatment alleviated the negative effects of drought stress on gas exchange by altering physical biochemical responses, which caused a low internal CO2 concentration, sucrose and leaf damage. The above findings show that, P. indica and NPs can mitigate the photosynthetic limitations through promoting photosynthetic capacity under drought stress in soybean.