PLASMOLYSIS 



135 



cell wall has ceased as, unlike the latter, the protoplasm has no lower limit 

 of elasticity. At this point, therefore, the protoplasmic layer will begin to 

 separate from the cell wall. If the hypertonic solution is strong enough this 

 separation of the protoplasm from the cell wall will become very pronounced. 

 In some types of cells the protoplasm will "ball up" into a more or less 

 spherical mass within the cell. More often the shrunken protoplasm assumes 

 other configurations as shown in Fig. 27. This phenomenon is called plasmol- 

 ysis. The pattern followed by the shrinkage of the protoplasm in plasmolysis 

 is more or less typical for each kind of cell, although it may be modified 



Fig. 27. Several common types of plasmolysis (diagrammatic), 



somewhat depending upon physico-chemical conditions within the protoplasm, 

 kind of solute used in the plasmolyzing solution, etc. The space bet\veen 

 the cell wall and the protoplasm will be filled, after the separation of the 

 latter from the wall, with the external solution. 



If a plasmolyzed cell is immersed in water it will slowly recover and 

 regain a turgid state, due to osmotic movement of water into the cell sap. 

 Similarly if immersed in a solution hypotonic to the cell sap recovery will 

 also ensue, but the degree of turgidity attained will be less than if the cell is 

 immersed in pure water. Rapid "deplasmolysis," however, results in the 

 death of many kinds of plant cells (Iljin, 1934). 



In the preceding discussion plant cells have been considered purely as 

 osmotic systems and we will continue to so regard them throughout the 

 chapter. Although this has been the prevailing concept — at least regarding 



