The joint effect of different concentration of Cd²⁺ and ionic liquid on the growth of wheat seedlings

The joint effect of different concentrations (0.05-0.375 mmol/L) of $Cd^{2+}$ and various concentrations (50-400 mg/L) of [$C_3mim$][OAc] on the growth and physiology of wheat seedlings were investigated. The toxicity of $Cd^{2+}$ could be significantly reduced by lower concentrations (50-200 mg/L) of [$C_3mim$][OAc]. With higher concentration (${\geq}300mg/L$) of [$C_3mim$][OAc], the reduction became less, and compared to $Cd^{2+}$ stress only, the toxicity of 400 mg/L [$C_3mim$][OAc] increased. As for different $Cd^{2+}$ concentrations, the optimal reduction depends on the balance between the exact concentration of $Cd^{2+}$ and [$C_3mim$][OAc]: With low $Cd^{2+}$ concentration (0.05-0.250 mmol/L) requiring 50 mg/L [$C_3mim$][OAc], it could reach a dynamic equilibrium, while high $Cd^{2+}$ concentration (0.375 mmol/L) requiring 100 mg/L [$C_3mim$][OAc]. The growth and physiological indexes of wheat seedlings show a decrease in toxicity compared to the Cd alone treatment, when the dynamic equilibrium is reached. The concentration of $Cd^{2+}$ in leaf tissues showed that low concentration (50-200 mg/L) of [$C_3mim$][OAc] can reduce the toxicity of $Cd^{2+}$ (0.05-0.375 mmol/L) by decreasing the level of $Cd^{2+}$ concentration in the tissues, whereas the higher concentration (${\geq}300mg/L$) of [$C_3mim$][OAc] can increase the concentration of $Cd^{2+}$.