Intracellular and Intercellular Compartmentation

From the above, it follows that plants growing in saline environments and accumulating high concentrations of salts must have a mechanism that facilitates high rates of metabolic activity in the cytoplasm. Enzymes from halophytes were shown not to have any enhanced capacity to work at high salt concentrations compared with those from glycophytes (1,171–176). This observation led to the hypothesis that toxic inorganic salts might be preferentially accumulated in vacuoles, where they could still have an osmotic role. In this intracellular-compartmentation model (17,177–179), the osmotic potential of the cytoplasm is adjusted by the accumulation of ‘compatible’ organic solutes such as glycinebetaine, proline, and cyclitols (27,171,173,177,180–184). For the interpretation of plant-sodium contents in saline environments, it is not therefore sufficient to know how much sodium a plant tissue contains. It is also necessary to consider the relative and absolute concentrations within different parts of the tissue, both at the inter and intracellular levels (178).