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The below mentioned article provides a study note on the plasmolysis in plant cell.
In many plant cells, the protoplasm may shrink completely away from the cell wall and collect as a spherical mass in the centre or in one corner of the cell (Fig. 665).
This phenomenon is called plasmolysis. When this contraction or withdrawal of protoplasm away from the cell wall has just commenced, i.e., when the turgour or the hydrostatic pressure on the cell wall has just been released (turgour is zero), the cell is then said to be at incipient plasmolysis or threshold plasmolysis.
The pattern followed and set up by shrinking protoplasm seems to be typical for each kind of cell (Fig. 665) although it can be modified to certain extent by the physiological condition of cell at that time.
The space between the cell wall and the contracting protoplasm will be filled up by the external solution as the cellulose cell wall without the adhering protoplasmic layer, is now permeable to both the solvent and solute alike and not differentially permeable.
In such a plasmolysed plant cell the release of turgour from the cell wall increases evidently the suction pressure of the cell, and the suction pressure being now freed from any other imposed pressure upon it, becomes equal to the osmotic pressure of the cell sap.
Evidently, such a cell will potentially have the maximum water absorbing capacity for both the osmotic and suction pressures are now equal in magnitude. If such a plasmolysed cell is transferred from hypertonic solution and to pure water, it will slowly recover by the net inward movement of water (if deplasmolysis, as it is sometimes called or inward movement of water, is too rapid, it may result in the death of the cell due to sudden stretching of protoplasm) subjecting the cell wall to a progressively imposed turgour pressure and in consequence, reducing the suction pressure of the cell.
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When the turgour pressure becomes equal to the osmotic pressure, the suction pressure of such a cell is zero and the cell has taken up the maximum amount of water from the surrounding medium. Such a cell is known as turgid and the phenomenon associated with it, turgidity.
Plasmolysis can be conveniently demonstrated in plant cells under microscope containing coloured (blue or red anthocyanins) cell sap since the contracting protoplasm can now be readily distinguished in the cell matrix.
