Responses of Crop Plants to Soil Salinity

The growth and yield formation of crop plants on saline soils may be hampered by osmotic stress, ion toxicity, and/or nutrient deficiency. To understand the complex physiological responses of crop plants to salt stress, a three-phase model of growth responses to salt stress was introduced. This is a conceptual model that integrates time, stress intensity and other environmental factors, and genotypical characters. Phase 0 describes a shock reaction after a sudden increase of the salt concentration in the root medium. This phase does not characterize traits for breeding purposes and should be avoided by acclimation. Phase I shows osmotic acclimation and avoidance of plant water deficit. It is appropriate to identify processes, enzymes, and genes that may limit in overcoming the osmotic stress. The appearance of ion toxicity symptoms such as chlorosis and necrosis is the start of Phase II. In this phase, ion toxicity, mainly caused by Na+, governs plant reaction to salt stress. In many dicotyledonous species, Cl− toxicity may add to the damage. In experimentation, it is important to consider that reactions in Phase I persist in Phase II.