Plants absorb water and minerals salt from the soil with the help of root hairs. They absorb water by the process of osmosis. Osmosis is the movement of water molecules (solvent) from a lower concentration solution to a higher concentration solution through a semi permeable membrane.

Root Hair Absorption Process: Osmosis

Osmosis is the process by which water molecules move across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In the case of root hair absorption, water is absorbed by the root hairs through osmosis.

Root Hairs and Their Function

Root hairs are tiny, finger-like projections that extend from the epidermal cells of plant roots. They greatly increase the surface area of the root, allowing for more efficient absorption of water and minerals from the soil. The root hairs are in close contact with the soil particles, which contain dissolved nutrients and water.

Process of Root Hair Absorption

The process of root hair absorption can be explained in the following steps:

1. Water Potential Gradient: The soil solution has a higher water potential compared to the root hair cell's cytoplasm. Water potential is the tendency of water to move from one area to another. The water potential gradient between the soil and the root hair cell creates a driving force for water movement.

2. Selective Permeability: The plasma membrane of the root hair cell acts as a selectively permeable membrane. It allows water molecules to pass through but restricts the movement of solutes and ions.

3. Solute Concentration in Root Hair Cell: The root hair cell has a higher solute concentration compared to the soil solution due to the presence of dissolved minerals and ions inside the cell.

4. Osmosis: Water molecules move from the soil solution into the root hair cell through osmosis. This occurs because the solute concentration inside the root hair cell is higher than the solute concentration in the soil solution. The water molecules move along the water potential gradient, from an area of lower solute concentration (soil solution) to an area of higher solute concentration (root hair cell).

5. Root Hair Cell Expansion: As water enters the root hair cell through osmosis, the cell expands, creating turgor pressure. This pressure helps to push the water further into the root and facilitates its movement through the plant.

Conclusion

In summary, the root hair absorbs water through the process of osmosis. The root hairs have a higher solute concentration inside the cell compared to the soil solution, creating a water potential gradient. Water molecules move from the soil solution into the root hair cell through osmosis, facilitating the absorption of water and nutrients from the soil.

Water comes in from the high concentration outside into the low concentration inside