Sandra Schmöckel, David Jarvis. Salt Stress. Encyclopedia of Applied Plant Sciences (Second Edition). http://dx.doi.org/10.1016/B978-0-12-394807-6.00086-1
Soil salinity is an abiotic stress that poses a great threat to agriculture. Major crop losses annually occur due to toxic salts in the soil, particularly sodium chloride (NaCl). When plants are stressed with NaCl, they often exhibit slower growth, premature leaf senescence, reduced tillering or branching, and decreased yield. Na+ is particularly detrimental in high concentrations in the cytosol of leaf cells, because Na+ interferes with metabolic processes such as photosynthesis. Hence, some plants have evolved tolerance mechanisms to prevent high concentrations of Na+ in the cytosol in leaves. The three main mechanisms include tissue tolerance, osmotic tolerance, and ion exclusion. In order to avoid yield losses due to soil salinity, crops are being developed that are able to tolerate salinity stress. Conventional breeding and genetic engineering are two main technologies currently used to generate crops with improved salinity tolerance.