Seed treatment with nano-iron (III) oxide enhances germination, seeding growth and salinity tolerance of sorghum

In recent decades, nanoparticles have been intensively applied in agriculture. Two experiments were carried out to demonstrate the potential of nano-iron oxide (n-Fe2O3) as seed treatment (soaking and priming) at different concentrations (0, 10, 50, 100 and 500 mg/L) for enhancing sorghum (Sorghum bicolor (L.) Moench) germination and seedling growth under non-stressed conditions (Experiment I), and to investigate the impacts of n-Fe2O3 seed priming treatments (0, 10, 50, 100 and 500 mg/L) on growth, chlorophyll content, chlorophyll a fluorescence, gas exchange, water relations and lipid peroxidation under salt stress (150 mmol NaCl solution) (Experiment II). Results indicated that seed soaking with n-Fe2O3 at 10 mg/L was the best treatment in improving speed and per cent of germination, while seed priming with n-Fe2O3 at 50 and 100 mg/L was the most effective treatment in improving seedling (12 days old) growth. Salt stress decreased chlorophyll content, photosynthetic rate, stomatal conductance, transpiration rate, relative water content, osmotic potential and growth, along with increased lipid peroxidation. Among chlorophyll a fluorescence parameters, the photosynthetic performance index of PSII (PIABS) was the most salt-responsive. Seed priming with n-Fe2O3 at 500 mg/L increased sorghum growth (45 days old), through increased photosystem II efficiency, chlorophyll index, photosynthetic rate and relative water content with decreased lipid peroxidation. Overall, this study indicated that use of n-Fe2O3 as a pre-sowing seed treatment can enhance germination and seedling growth of sorghum and protect from negative impacts of salinity stress.