Osmotic adjustment in plants is a physiological process that helps them maintain water balance and survive under drought or saline conditions. It involves the accumulation or reduction of solutes in plant cells to regulate water potential.
Mechanism of Osmotic Adjustment:
1. Solute Accumulation:
Plants accumulate organic (sugars, amino acids) and inorganic (potassium, chloride) solutes in their cells.
These solutes help lower the water potential inside the cells, allowing water to move in and preventing dehydration.
2. Turgor Maintenance:
Osmotic adjustment ensures that cells maintain turgor pressure, which is crucial for cell expansion, stomatal regulation, and overall plant growth.
3. Drought and Salinity Tolerance:
During drought, plants adjust their internal solute concentration to retain water and continue metabolic activities.
In saline conditions, they prevent excessive salt accumulation by maintaining higher intracellular concentrations of compatible solutes like proline and glycine betaine.
4. Role of Hormones:
Abscisic acid (ABA) plays a key role in triggering osmotic adjustment during water stress, leading to stomatal closure and reduced water loss.
Osmotic adjustment enhances plant survival by improving drought resistance, regulating water uptake, and maintaining cell structure even in challenging environmental conditions.