Osmotic adjustment or Osmoregulation - Osmotic Stress
If concentration of soluble matter (in the form of minerals and small organic molecules) builds up in the external medium, it will create a gradient demanding outward movement of water from the plant cells, thereby causing dehydration. Alternatively, it will create a pressure on the cells to take in the solutes and maintain osmotic equilibrium with its immediate environment. You will appreciate that no - organism can freely take these options indiscriminately.
Hence, many of them accumulate certain compatible solutes within the cells to attain osmotic equilibrium with their immediate surroundings. In general proline and glycinebetaine are important organic molecules that help bacterial and plant cells to alleviate such osmotic stress. The build up of carbohydrates, amino acids, polyhydric alcohol and other molecules due to water stress or high salt concentration is called osmotic adjustment or osmoregulation.