It is present in plant cells only and it surrounds cell membrane.It is made up of cellulose as a major component in contrast the fungal cell wall is made up of chitin. Along with cellulose the cell wall is composed of pectin ,hemicellulose, protein and water.
# Cell wall formation occur in the form of cell plate at the time of cell division.
PHYSICAL STRUCTURE: The cell wall have two regions primary and secondary cell wall but in some plants a third layer add on called tertiary cell wall.
| PRIMARY CELL WALL | SECONDARY CELL WALL | TERTIARY CELL WALL |
| 1.Young plant cell form a single layer cell wall called primary cell wall. 2.Growth of primary cell wall takes place by intussusception*. 3.Meristematic,parenchymatus,leaves and fruit cell have primary cell wall. 4.It is flexible. | 1. In mature cells more wall material added on to the primary wall these new layers are called secondary walls these are S₁ S₂ and S₃. 2. Growth of secondary cell wall by accretion*. 3. Harder woody parts of plants Sclerenchyma Collenchymas fibres ,vessels,and tracheids have secondary walls. 4.It is rigid. | 1.Tracheids of gymnosperm have another layer of cellulose and xylan internal to secondary wall. |
MIDDLE LAMELLA : It is the first layer of cell also called cementing material between two cells .It is absent on the outer exposed surface of the cells .It is composed of calcium and magnesium pectate.
In ripen fruits the softness is due to pectate compound of middle lamella.
PITS: These are two types simple pits and bordered pits.
| SIMPLE PITS | BORDERED PITS |
| At certain places secondary wall is not formed on primary walls these are simple pits composed of primary wall and middle lamella. | In tracheids of gymnosperms the secondary wall overhangs on pits these are bordered pits. |
*Intussusception : Growth by addition of more growth material within existing one.
*Accertion:Growth by addition of new wall material on the existing one.
