Plants as sessile organisms cannot escape from negative effects imposed by detrimental environments such as high salinity, drought, freezing, high temperature, and flooding. Soil salinity has increasingly become one of major abiotic stresses that constraint plant growth worldwide (Frommer et al., 1999). In nature, soil salinity and alkalinity often occurs simultaneously due to the complexity of soils (Zhang et al., 2015). Approximately half of the saline soils in earth’s crust contain NaHCO3 and Na2CO3, which are the main factors that contribute to soil alkalinity (Yang et al., 2009). Excess Na+ and high pH value in saline–alkaline soils cause considerable damages to plant growth and development, whereas most plant species are more susceptible to high pH soils (more than 8.0) than saline soils (Tang et al., 2014; Li et al., 2016). High soil pH adversely affects seed germination, root cell structure and functions, the availability and absorption of nutrient elements, thereby leading to a remarkable decrease in crop yield and quality (Tang et al., 2014; Zhou et al., 2016a). According to the statistics, there is more than 800 million hectare of saline–alkaline soils in the world (Martinez-Beltran and Manzur, 2005). Hence, it is an urgent need to develop effective strategies to enhance the ability of plants to tolerate saline–alkaline conditions.