Plasmolysis And Deplasmolysis
PLASMOLYSIS AND DEPLASMOLYSIS
Plasmolysis is the process of shrinkage
or contraction of the protoplasm of a plant cell as a result of loss of water
from the cell and deplasmolysis is swelling of the protoplasm due to gain of
Plasmolysis and deplasmolysis occurs due to the passage of water from higher water concentration to lower water concentration through a semipermeable membrane. Water molecules constantly move inside and outside the cell across cell membranes. This free flow of water has the very important consequence of enabling cells to absorb water.
Plasmolysis is one of the results of osmosis and occurs very rarely in nature, but it happens in some extreme conditions. Normally Rheo or Tradescantia plant epidermal cell are used for experiment because they have coloured cell sap which can be clearly visible.
Plasmolysis (hypertonic sol):
When a plant cell is placed in concentrated salt solution, water concentration inside the cell is greater than that which is outside the cell. Therefore, water moves through the cell membrane into the surrounding medium (exosmosis). Ultimately the protoplasm separate from the cell wall and assumes spherical shape. This is called plasmolysis.
Deplasmolysis (hypotonic sol):
When a plasmolysed cell is placed in a hypotonic solution, (i.e., the solution having solute concentration lower than the cell sap), the water moves into the cell because of the higher concentration of water outside the cell than in the cell (endosmosis). The cell then swells to become turgid. It is called deplasmolysis.
If we place living cells in isotonic solution (i.e., both solutions have the same amount of solute concentration), there is no net flow of water towards the inside or outside. Here, the water moves in and out of the cell and is in equilibrium, so the cells are said to be flaccid
Internal and external factors greatly affect plasmolysis form and plasmolysis time. The most important cell factors affecting plasmolysis are-
- cell wall attachment
- protoplasmic viscosity, and, for some cell species,
- cell wall pore size.
These factors vary greatly with cell type, plant age, and stage of development.
De plasmolysis is the opposite process of plasmolysis; when the concentration of the solution external to a plasmolyzed cell is decreased or when solutes permeate from the external solution into the vacuole, water will reenter the vacuole, and the increase in protoplast volume leads to restoration of full turgidity.