In this study,the seedlings of the wetland emergent plant,Canna generalis Bailey,were used as the experimental materials.Pretreatment of the seedlings with 150 μmol/L MgCl₂ was conducted under the greenhouse conditions for 12 h.Subseqently,treatment of the seedlings with farmland wastewater containing 10 mg/L nitrate (NO₃--N) was performed to investigate the effects of MgCl₂ pretreatment on the nitrate absorption efficiency,the plasma membrane H⁺-ATPase and H⁺ pump activities and the interaction of plasma membrane H⁺-ATPase and 14-3-3 protein of C.generalis in farmland wastewater.The results showed that pretreatment of 150 μmol/L MgCl₂ for 12 h increased the nitrate absorption efficiency of C.generalis Bailey in farmland wastewater by 11%.Compared with those in the roots of the plants without MgCl₂ pretreatment,both the plasma membrane H⁺-ATPase and H⁺ pump activities in C.generalis roots with MgCl₂ pretreatment were significantly elevated.MgCl₂ pretreatment also enhanced plasma membrane H⁺-ATPase and 14-3-3 protein interaction in C.generalis roots.These results suggested that MgCl₂ pretreatment increased the Plasma membrane H⁺-ATPase activity by enhancing its interaction with 14-3-3 protein,thereby increasing the nitrate absorption efficiency of C.generalis in farmland wastewater.