Role of calcium in plants under salt stress

The role of Ca in preserving the structural and functional integrity of plant cell membranes, stabilization of cell wall structures and in regulation, transport and control of ion exchange behaviour is well documented. However, recently Ca has attracted attention as a second messenger in the signal conduction between environmental factors and plant responses. These functions are seriously impaired by reduced Ca2+ availability under saline and particularly sodic conditions. The uptake of Ca2+ from soil solution may decrease because of ion interactions, precipitation and increases in ionic strength that reduce the activity of Ca2+ leading to reduced growth and yields, under saline conditions. The available information on plant responses to nutritional imbalances due to high Na+/Ca2+ ratios under salinity conditions has been discussed and the mechanisms governing sodium- calcium interactions in plants have been outlined.