Abstract: Cadmium (Cd) is a kind of highly toxic heavy metal element which exists in nature for long time. Titanium dioxide nanomaterials (TiO₂ NPs) are a new type of nanomaterial widely used in various fields due to special surface properties, which inevitably enter the environment to coexist with Cd. The coexistence of Cd and TiO₂ NPs in soil would affect plant growth. In this study, we conducted morphological, cytological, subcellular observations and physiological and biochemical measurements on Salix matsudana Koidz. seedlings under the single or combined treatments of Cd and TiO₂ NPs in soils. The results showed that Cd and TiO₂ NPs alone inhibited the growth and development of S. matsudana, produced peroxide damage, reduced photosynthesis, and altered the distribution of Cd in tissues and subcells. Low concentrations of TiO₂ NPs in coexistence with Cd reduced the biotoxicity of Cd by changing the subcellular distribution of Cd, and alleviated the peroxidative damage and photosynthesis inhibition of Cd on S. matsudana. In contrast, high concentrations of TiO₂ NPs coexisted with Cd increased the distribution of Cd in organelle fractions, aggravated Cd toxicity to plants, and inhibited plant growth. Therefore, the appropriate concentration of TiO₂ NPs can alleviate the toxic effect of environmental Cd stress on S. matsudana and improve its phytoremediation efficiency. Our findings provide theoretical basis for the application of S. matsudana in phytoremediation.

Key words: Salix matsudana Koidz., cadmium, titanium dioxide nanoparticles, phytoremediation