Chemical Modification of Cell Wall


Chemical Modification of Cell Wall            


  • In almost all plants cell walls are mainly made up of cellulose. 
  • But to provide mechanical support other cellular substances viz, lignin, cutin, suberin, pectin and mineral are also deposited.
  • So the cell wall becomes chemically modified. 
  • The following conditions may occur in cell wall after primary wall formation.
  • It is the following type-

1. Lignification: 

  • Lignin is a complex and hard substance which makes their delicate primary wall lignified, thickened, rigid and hard together with cellulose.
  • Lignin Is impermeable to water. 
  • Those cells which undergo lignification, are dead, and provide mechanical strength. 
  • The protoplasm of lignified cells ultimately is lost completely for example vessels, tracheids and sclerenchyma etc. a

2. Suberization

  • It is a mixture of many fats. 
  • It is produced by the condensation of glycerol and phenolic acids. Which is impermeable to water.
  • Suberin normally accumulates at middle lamella. This process is called suberization.
  • By the deposition of suberin cell are dead.
  • It is found in Cork cells and casparian srips.

3. Cutinization : 

  • It is a waxy material which is an anhydrous form of fatty acids.
  • It is also impermeable to water 
  • This is present on epidermis of aerial parts of plants as a single layer. This layer is called cuticle. The accumulation of cuticle or its formation is called cutinization 
  • It helps In prevention of evaporation. 
  • Sometimes a wavy layer is formed over the cuticle called bloom which also controls evaporation. 
  • The thickness of cuticle varies in all plants according to the environment. 

4. Deposition of cellulose

  • The wall of plant cells are formed initially by cellulose. But some time it is thickened by the cellulose 
  • For example, collenchyma and cotton fibres are made from cellulose. 

5. Formation of Pectin

  • After the fruit ripen the chemical composition of cell wall is changed.
  • In these cells Middle lamella is composed of Ca and Mg Pactat and Primary cell wall and Secondary cell wall are composed of cellulose and pactose.
  • After the ripen of fruit pectin is formed in these cell walls which are soluble.

6. Mucilage formation : 

  • In certain conditions cellulose is decomposed into mucilaginous substance which is called mucilage. 
  • It has the ability to absorb water hence it is converted into viscous fluid by absorbing water. 
  • The cell wall of leaves of Aloe Vera, Chinarose, fruits of lady finger, isabgol etc. possess a major content of mucilage in them.

7. Mineralization : 

  • Minerals and salts such as silica, calcium carbonate, calcium oxalate etc are accumulated in plant cells so that cells become rigid. 
  • Silica is found  in high amounts in equisetum plants (Pteridophyta) and grass leaves. 

8. Deposition of other substances: Substance like resin and tanin are present in some plants.

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