Before explaining Plasmolysis, it is important to know something about plant cell anatomy. Plant cell consists of thick wall known as cell wall. The cell holds them upright and prevents from losing their shape. The plasma membrane lies under the cell wall and holds the goop within the cell which is known as cytoplasm. All the major parts of the cell function together to keep the plant active. The vacuole is located in the cytoplasm that holds the water in the plant cell.
Plants do not get sufficient water during plasmolysis. The plasma membrane and cytoplasm shrivels and pulls apart from the cell wall, causing the complete plant to shrink.
What is Plasmolysis?
Plasmolysis is defined as the process of contraction or shrinkage of the protoplasm of a plant cell occurred due to loss of water in the plant cell. It is one of the outcomes of osmosis and rarely occurs in nature. We can involve plasmolysis experiment in the laboratory by placing a living cell in a strong salt solution to loose water from the cell. Normally we use Tradescantia or Rheo plant cell for the experiment since they have colored sap which is easily visible.
How does the water pass through cell membranes?
The cell membrane separates the interiors of the cell from the surrounding. It allows water molecules, ion or some particles across the membrane and stops others. Water molecules travel in and out of the cell across cell membranes. This water flow is a necessary consequence that enables cells to fetch water.
Demonstration of plasmolysis in peels of the Rheo plant
Plasmolysis and deplasmolysis
When you place a plant cell in concentrated salt solution, because of osmosis,water from the cell sap moves out.
The concentration of water inside the cell is higher than outside the cell. Therefore, the water travels through the cell membrane into the neighbouring medium. Finally, the protoplasm separates from the cell and assumes a spherical shape. This is known as plasmolysis.
When you place a plasmolysed cell in a hypotonic solution, (the solution in which solute concentration is less than the cell sap), the water travels into the cell due to the higher concentration of water outside the cell. Then the cell swells and becomes turgid. This is known as deplasmolysis.
When the living cells are placed in isotonic solution(both solutions have the equal amount of solute particles), the water does not flow within or outside. Here, the water passes in and out of the cell and in an equilibrium state, and Therefore, the cells are called as flaccid.
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