Combined effects of carbon nanotubes and cadmium on the photosynthetic capacity and antioxidant response of wheat seedlings.

A detailed study of nanomaterials has revealed their broad application prospects. However, the presence of carbon nanotubes (CNTs) in the environment has been increasing and has aroused concerns regarding their toxicity to crops when combined with heavy metals. In the present study, the effects of Cd on the photosynthetic capacity and antioxidant activity of wheat seedlings in the presence of single-walled CNTs (SW) and multi-walled CNTs (MW) were investigated. Our results indicated that SW (5-40 mg L) and MW (10-40 mg L) significantly increased the oxidative stress response of wheat seedlings to Cd. Compared with Cd alone, CNTs combined with Cd decreased net photosynthetic rate, stomatal conductance, transpiration rate, primary maximum photochemical efficiency of photosystem II, actual quantum yield, photosynthetic electron transport rate, root canal protein, and ribulose-1,5-bisphosphate carboxylase/oxygenase content. Moreover, combined treatments increased the content of superoxide anion, superoxide dismutase, guaiacol peroxidase, cytochrome, and malondialdehyde in wheat seedlings. Moreover, membrane lipid peroxidation was aggravated, causing serious damage to the wheat membrane system. In addition, the toxicity of the SW treatment and the combined treatment with SW and Cd was higher than that of the MW treatment.