Toxicity of Zinc Oxide and Titanium Oxide Nanoparticles on Lentil, Wheat, and Bean Seeds

Aim: 
Zinc oxide (ZnO) and titanium oxide (TiO₂) nanoparticles are used on a commercial scale in many countries. Despite numerous studies on the toxicity of nanoparticles, few have addressed their toxicity in edible grains. The aim of this study was to investigate the growth inhibition of ZnO and TiO₂ nanoparticles on lentil, wheat, and bean seeds.
Methods: 
The ZnO and TiO₂ nanoparticles were investigated using transmission electron microscopy. Different concentrations of ZnO and TiO₂ nanoparticles (0.1, 1, 10, 100, and 1000 mg/l) were prepared in distilled water for irrigation of lentil, wheat, and bean seeds. The seeds were irrigated three times a day for 8 consecutive days, with 3 ml of solution per irrigation. To determine the toxicity of nanoparticles, the number of germinated seeds was counted, and the stem lengths were measured using a caliper. Data were analyzed to calculate the 50% lethal concentration (LC₅₀).
Results: 
Exposure to all concentrations of both nanoparticles resulted in growth reduction in lentil seeds. Bean seeds showed decreased growth with ZnO nanoparticles and increased growth with TiO₂. Wheat seeds exhibited both growth increases and decreases at nanoparticle concentrations.
Conclusions: 
This study showed that the toxic effect of nanoparticles depends on both the type of nanoparticle and the seeds. Furthermore, the concentration of nanoparticles plays a significant role in their toxicity. Therefore, more research is needed to explore the effects of different nanoparticles on plants in various growth environments to better understand their toxic effects on plant organs and their impact on plant growth and development.