Osmosis is thought to be a special type of diffusion and may be defined as the diffusion of the solvent (e.g. water) through a differentially permeable membrane from an area where it is in high concentration to an area where it is in low concentration.
This diffusion continues until the two solutions become equal in concentration.
Osmosis is of two kinds:
Endosmosis: The flow of solvent from out side of a cell to the inside of the cell. By this process, the plant absorbs water through root hair.
Exosmosis: The flow of solvent from inside of the cell to the out side of the cell. By this process plasmolysis of the cell occurs.
The significance of Osmosis in plant life:
1. Water absorption: Plant absorbs water from the soil through osmosis.
2. Diffusion: Entering of water from one cell to another is also regulated by osmosis.
3. Equal distribution of water: Equal distribution of water to different organs such as- leaf, stem, root etc. is mainly performed by osmosis.
4. Turgidity of cells: Osmosis is responsible for the turgidity of cells.
5. Regulation of the rate of transpiration: Osmosis has the active participation in regulating the rate of transpiration.
6. Dispersion of fruit and seed: Osmosis indirectly helps in the dispersion of fruit and seed.
7. Movement of different organs: The movement of different organs of the plant such as the opening as well as the closing of stomata of leaves is dependent on osmosis.
8. Self-defence: Plants can stand against the adverse condition of the environment like drought salinity snow falling due to increasing of osmotic pressure.
9. The growth of the plant body: Osmosis indirectly helps in cell division by creating turgidity as a result of which growth of the plant body is performed.
10. Germination: Osmosis plays a notable role in germinating seeds and spores.