The capacity of plants to maintain a high cytosolic K+/Na+ ratio is likely to be one of the key determinants of plant salt tolerance. Important progress has been made in recent years regarding the identification and characterization of genes and transporters that contribute to the cytosolic K+/Na+ratio.
Plant growth depends on the supply of inorganic nutrients.Typically, plants are exposed to nutrient levels that vary widely in both time and space. To cope with such fluctuating
environments plants have developed high levels of plasticity both at the individual level and within species and ecotypes.Nevertheless, extreme nutrient conditions will cause de- ®ciency or toxicity to a varying extent for different plant species. This notion is clearly explained in the different degrees of salinity tolerance found in various plant species. Significant entry of Na+ will result in severe growth reduction or death in salt sensitive or glycophytic species, will lead to mild toxicity symptoms in salt tolerant species, but may benefit halophytes.
