Exposure to low levels of photocatalytic TiO nanoparticles enhances seed germination and seedling growth of amaranth and cruciferous vegetables.

Titanium dioxide (TiO) is one of the most common compounds on Earth, and it is used in natural forms or engineered bulks or nanoparticles (NPs) with increasing rates. However, the effect of TiO NPs on plants remains controversial. Previous studies demonstrated that TiO NPs are toxic to plants, because the photocatalytic property of TiO produces biohazardous reactive oxygen species. In contrast, another line of evidence suggested that TiO NPs are beneficial to plant growth. To verify this argument, in this study, we used seed germination of amaranth and cruciferous vegetables as a model system. Intriguingly, our data suggested that the controversy was due to the dosage effect. The photocatalytic activity of TiO NPs positively affected seed germination and growth through gibberellins in a plant-tolerable range (0.1 and 0.2 mg/cm), whereas overdosing (1 mg/cm) induced tissue damage. Given that plants are the foundations of the ecosystem; these findings are useful for agricultural application, sustainable development and maintenance of healthy environments.