The Effect of Different Levels of Titanium Dioxide Nanoparticles in Soil on Sorghum Growth Characteristics

Titanium dioxide nanoparticles (TiO2 NPs) are being used widely for different purposes such as plant science and environmental remediation. Soil remediation using TiO2 NPs with the aim of minimizing their toxicity in plants requires sufficient knowledge about the fate of these nanoparticles in the soil. Excessive amounts of nanomaterials may pose inhibitory effects on the growth of plants cultivated in TiO2 NPs-affected soils. The main aim of this study was to investigate the effect of different levels of TiO2 NPs in soil on sorghum (Sorghum bicolor) growth and the fate of these nanoparticles in plants. Sorghum seeds were sown in plastic pots containing different concentrations of TiO2 NPs. Sorghum was found to be a tolerant plant species in the presence of TiO2 NPs in soil; however, addition of higher doses of TiO2 NPs (i.e., 800 and 1000 mg kg-1 soil) adversely affected seed germination and plant growth. Results indicated that the total titanium (Ti) contents in sorghum treated with nanoparticles increased compared to the control. Significantly higher accumulation of Ti in the root compared to the shoot of sorghum was observed in all of the treatments. Results indicated that the total Ti contents in the plants treated with TiO2 NPs were higher than those in control, with the highest Ti accumulation capacity of 21.32 mg per pot obtained in the soil treated with 500 mg kg-1 TiO2 NPs. Toxicity of higher doses of TiO2 NPs to the plants was observed in this study. The results showed that sorghum has an acceptable tolerance in the low to moderate concentrations of TiO2 NPs, whereas the high concentrations of these nanoparticles have inhibitory effects on the sorghum growth. Selection and application of proper doses of nanomaterials may prevent their negative effects on affected plants, while promoting the plant phytoextraction ability.