ABSTRACT
Abstract. Soil salinity is one of the most emergent environmental problems in the world, which limits crop yield and productivity seriously. Today, about 20% of the world’s cultivated land and nearly half of all irrigated lands are affected by salinity (Rhoades and Loveday, 1990). Salt in the soil may lower water potential in the soil and decrease water absorption ability of the plant; salt accumulation in the plant shows lower growth rate and photosynthetic rate, together with damaging syndromes. There are different hypotheses about salt injury and salinity tolerance mechanisms of plants, yet reactive oxygen species (ROS) are regarded as the main source of oxidative damage to cells under salinity stress as well as other environmental stresses such as drought, high temperature, chilling, and flooding. To scavenge the ROS, plants require the activation
of complex metabolic activities including antioxidative pathways, of which ascorbate (AsA)– glutathione (GSH) cycle plays a very important role, both enzymatically and nonenzymatically. AsA-GSH cycle was first put forward by Noctor and Foyer (1998), which operates in the cytosol, mitochondria, plastids, and peroxisomes (Noctor and Foyer, 1998). Since GSH, AsA, and NADPH are present in high concentrations in plant cells, it is assumed that the AsA-GSH cycle plays a key role in ROS detoxification. In this chapter, the production of ROS, the family of AsA-GSH cycle, and the role of AsA-GSH cycle in plant salt tolerance are discussed, respectively.
