Physiology and biochemistry of salt stress tolerance in plants.

Salinity is one the major environmental stresses affecting crop production worldwide. The salt effects on plants include osmotic stress, ion toxicity, nutrient imbalance and deficiencies, resulting in membrane damage, decreased cell expansion and division, changes in metabolic processes, oxidative stress and genotoxicity. Thus plant salt tolerance is a highly complex phenomenon that involves alterations in physiological and biochemical processes, which may result in morphological and developmental changes. In this scenario, the regulation of uptake, transport and compartmentation of Na+ and Cl-, biosynthesis of compatible solute and specific proteins, reduction of reactive oxygen species formation and increase of antioxidant defence system have been related as important mechanisms for salt tolerance. In this chapter, we give an overview of the physiological, biochemical and molecular mechanisms underlying salt tolerance, combining knowledge from classic physiology with recent findings. Special emphasis will be given on salt signal perception and transduction and mechanisms related to maintenance of osmotic, ionic, biochemical and redox homoeostasis in salt-stressed plants. A fundamental biological knowledge in conjunction with understanding about the effects of salt stress on plants is essential to supply additional information for a thorough analysis of the plant salt-tolerance mechanisms and reduce the deleterious effects of salinity on plants, improving crop productivity important to agricultural sustainability.