Role of nitric oxide in improving plant resistance against salt stress

Soil salinity is a serious threat to agricultural production worldwide. Salinity imposes both osmotic stress and ionic toxicity to plants which have adverse effects on cytosolic enzyme activities, nutritional disorders and oxidative damage, resulting in drastic yield reductions. Salinity resistance in plants is determined by the physiological processes improving water uptake and retention, maintenance of ion homeostasis and protection from oxidative stress. Nitric oxide (NO), an important signaling molecule, plays a pivotal role in improving salinity resistance through the production of osmolytes, specific proteins, controlling water flux, ion homeostasis and activation of antioxidant defense system. There is also emerging evidence, although not extensive, that NO plays a systemic signaling role during the establishment of salt resistance in plants. In this chapter, the role of NO in osmoregulation, ion homeostasis and the antioxidant defense system under salinity stress are discussed. The involvement of NO in stress signaling and hormonal regulation is also discussed.