Salt Tolerance

(also salt resistance), in plants, the ability to grow on saline soils. The most salt-tolerant plants are halo-phytes; however, even these plants are very sensitive to sudden increases in salinity. Any plant can adapt to high salt content in the process of ontogeny. Adaptation depends on the type of salts. With chloride salinity, plants become fleshy, or succulent; with sulfate salinity, they usually acquire a xeromorphic structure (seeXEROMORPHISM).

The principal cause of damage to plants on saline soils is the toxicity of salts—not the high osmotic pressure, as was believed before the 20th century. When cultivating plants on soils with an increased content of chlorides, sulfates, or carbonates, the seeds should first be soaked in appropriate salt solutions to increase salt tolerance. With this kind of hardening, the protoplasm’s permeability to salts is lowered, its threshhold of coagulation by salts is raised, and its metabolism is changed. Plants growing on saline soils have demonstrated changes in nucleic-acid, protein, carbohydrate, and phosphorus metabolism.