Question

Distinguish between :
Primary wall and secondary wall

Answer 1

Primary wall	Secondary wall
Primary wall is laid inner to middle lamella.	Secondary wall is laid inner to primary wall.
It is formed in young growing cell.	It is formed when the cell has stopped growing.
It is capable of extension.	Extensibility is usually absent.
The wall grows by intussusception or addition of materials inside.	It grows by accretion or deposition of materials on the existing structures.
It is single layered.	Secondary wall is three or more layered.
Hydration is 60%.	Hydration is 30-40%.
Cellulose content is comparatively low.	Cellulose content is comparatively high.
Cellulose microfibrils are shorter, wavy and loosely arranged.	Cellulose microfibrils are longer, closely arranged, straight and parallel.
Protein content is high, upto 5%.	Protein content is low, 1% or less.
Hemicellulose content is high, upto 50%.	Hemicellulose content is 25% of the total.
Lipid content is 5-10%.	Lipid is absent or negligible.
Additional chemicals like lignin are absent.	Lignin, suberin, etc. are absent.
Primary wall is thin.	Secondary wall is quite thick.
Pits are usually absent in a primary wall.	Pits often occur in the secondary wall.