Salinity Stress: A Review

Salinity stress has a major impact on plant growth and development. Increasing concentrations of salt in farm soils means that researchers must develop tolerant crops if the global food supply is to be sustained. Salt adaptation involves a complex network of different mechanisms whose responses to high salinity are regulated in an integrated fashion. Plant growth responds to salinity in two phases: a rapid, osmotic phase that inhibits growth of young leaves, and a slower, ionic phase that accelerates senescence of mature leaves. Plant salt stress is a condition where excessive salts in soil solution cause inhibition of plant growth or plant death. On a world scale, no toxic substance restricts plant growth more than does salt. Salt stress presents an increasing threat to plant agriculture. Among the various sources of soil salinity, irrigation combined with poor drainage is the most serious, because it represents losses of once productive agricultural land. Salinity stress negatively impacts agricultural yield throughout the world affecting production whether it is for subsistence or economic gain. The plant response to salinity consists of numerous processes that must function in coordination to alleviate both cellular hyperosmolarity and ion disequilibrium. In addition, crop plants must be capable of satisfactory biomass production in a saline environment (yield stability). Tolerance and yield stability are complex genetic traits that are difficult to establish in crops since salt stress may occur as a catastrophic episode, be imposed continuously or intermittently, or become gradually more severe, and at any stage during development. However, cell physiology research is providing new insight into the plant response to salinity and is identifying genetic determinants that effect salt tolerance.