Potential of green synthesized titanium dioxide nanoparticles for enhancing seedling emergence, vigor and tolerance indices and DPPH free radical scavenging in two varieties of soybean under salinity stress

Background Considering titanium dioxide nanoparticles (TiO2 NPs) role in plant growth and especially in plant tolerance against abiotic stress, in the present work, TiO2 NPs were green synthesized using an aqueous solution of Aloe vera leaf extract as a capping agent and titanium tetrachloride as a precursor. These green synthesized TiO2 NPs were characterized using different techniques: UV spectrophotometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Results revealed that synthesized TiO2 NPs possess a tetragonal morphology with a size ranging from 10 to 25 nm. Additionally, the present work evaluated the effects of three concentrations of TiO2 NPs (0, 30 and 50 ppm) and six NaCl concentrations (0, 25, 50, 100, 150 and 200 mM) and their interactions with respect to germination parameters, vigor indices, oxidative stress and DPPH free radical scavenging of two varieties of soybean (Glycine max L. var. 22 and 35).Results Results demonstrated that all germination traits and vigor indices were negatively affected under all salinity levels. Also, the contents of hydrogen peroxide (H2O2) and malondialdehyde (MDA) were significantly increased by increasing the NaCl concentrations in two soybean varieties. Most interestingly, TiO2 NPs (30 ppm) mediated positive effects on germination parameters, reducing H2O2 and MDA contents by enhancing antioxidant (decreasing IC50) whereas 50 ppm showed an intermediate response under both control and saline soil conditions.Conclusion Our findings demonstrate the growth enhancement effects of TiO2 NPs application as well as its ameliorative potential in dealing with salinity.