The Plant Cell Wall

The plant cell wall is heterogeneous structure composed of layers (lamellae)
§  Each cell secretes its own wall
§  Junction between the walls is the Middle lamella
§  Cell wall is penetrated by plasmodesmata connecting neighbouring cells
§  Cell walls are primarily composed of sugar polymers i.e. polysaccharides
§  The architecture, mechanics, and function of plants depend crucially on structure of cell wall
·         Functions 
§  Regulates cell volume by limiting protoplast size preventing cell rupture
§  Determines cell shape
§  Involved in cell-cell adhesion; provide support to cells and whole plant
§  Forms specialized structures for:
§  Transport of water and nutrients
§  Defense against bacterial and fungal attack
§  Reproduction
·         Composition of Cell Walls
§  Primary cell wall:
§  Which is the only cell wall in growing and dividing cells
§  First formed cell wall
§  Composed of cellulose embedded in matrix of hemicelluloseand pectin, cellulosemolecules: Unbranched glucose chains and hemicellulose – a highly branched molecule of sugars and sugar derivatives
§  Pectins:
·         Are highly branched negatively charged polysaccharides rich in galacturonic acid
·         Give compressive strength to the cell wall
·         Modulate porosity, pH, and ion concentrations within the wall
§  Primary wall/Middle Lamellae
§  Primarily associated with hemicellulosesand pectins
§  Water is 65% of weight of cell wall
§  Secondary Cell Wall
§  Many plant cells synthesize secondary walls after the cell has completely elongated
§  Secondary wall is deposited by protoplast inside primary wall after cell stops growing
§  Composition of secondary wall:
·         Cellulose, hemicellulose and pectin
·         Lignin
·         Stronger than cellulose
·         There substances found on the surface of the cell wall. These include cuticle waxes, suberin and minerals
Blue Water Wallpaper


Evans, W. C. (2009). Trease and Evans Pharmacognosy. India: Reed Elsevier Limited.


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