Cellular Mechanisms of Plant Salt Tolerance

Salinity is a severe threat to agricultural production of over 80 million ha arable land area globally, especially in irrigated arid and semiarid regions. Understanding how plants cope with salt stress is therefore imperative. As the glycophytes and halophytes have salt tolerance mechanisms occur at the cellular level, understanding cellular mechanisms of salt tolerance becomes indispensable for crop improvement programs. Recent challenges such as climate change, increased world population, and demand for foods all over the globe aggravate the salinity impacts on plant production which urge scientists to understand deeply and fully the effects of salt stress on plants and how plants combat these effects. This chapter hence discusses the cellular mechanisms that may contribute to plant salt adaptation, namely, osmotic adjustment and osmolyte production, ion homeostasis and involvement of membrane transport systems, antioxidant defense systems and reactive oxygen species (ROS) detoxification, membrane lipids and proteins modeling to maintain membrane integrity, transport system activities, and signaling and cell wall modifications to regulate cell wall integrity, cell expansion, and stress sensing and signaling transduction. Disagreements among published data concerning these cellular mechanisms are also addressed. We believe that adopting one cellular mechanism for crop improvement programs or to understand plant adaptation to high salinity is not sufficient and premature. Alternatively, several genes must be pyramided to ensure the efficiency of any cellular salt tolerance trait, and testing hypotheses instead of just collecting repetitive data must be considered as promising feasible strategies to improve productivity in crop plants and unmask the puzzle of salt tolerance mechanism. Moreover, testing the results in realistic growth conditions such as the natural field saline conditions must be performed and focused in our future research in order to verify the underlying mechanism and its proposed functions in salt adaptation.