Toxicity of sulfadiazine and copper and their interaction to wheat (Triticum aestivum L.) seedlings

- The addition of Cu significantly inhibited the uptake of SDZ by wheat seedlings.
- Excess SDZ and/or Cu negatively affects growth of wheat seedlings due to oxidative damage.
- The combined effects of SDZ and Cu were different from those of single compound.
- The interactive effects of SDZ and Cu were mainly dependent on their relative toxicity.

A pot experiment was carried out to investigate the single and combined effect of different concentrations of sulfadiazine (SDZ) (1 and 10 mg kg−1) and copper (Cu) (20 and 200 mg kg−1) stresses on growth, hydrogen peroxide (H2O2), malondialdehyde (MDA), antioxidant enzyme activities of wheat seedlings and their accumulation. High SDZ or Cu level significantly inhibited the growth of wheat seedlings, but the emergence rate was only inhibited by high SDZ level. The presence of Cu reduced the accumulation of SDZ, whereas the effect of SDZ on the accumulation of Cu depended on their concentrations. Low Cu level significantly increased the chlorophyll content, while high Cu level or both SDZ concentrations resulted in a significant decrease in the chlorophyll content as compared to the control. Additionally, H2O2 and MDA contents increased with the elevated SDZ or Cu level. The activities of superoxide dismutase, peroxidase and catalase were also stimulated by SDZ or Cu except for the aerial part treated by low Cu level and root treated by high SDZ level. The joint toxicity data showed that the toxicity of SDZ to wheat seedlings was generally alleviated by the presence of Cu, whereas the combined toxicity of SDZ and Cu was larger than equivalent Cu alone.