The plant cells are bounded externally by a non-living, firm-covering called cell wall. The cell wall does not act as physiological boundary. The main function is mechanical, i.e. to provide protection and shape to the cell. The major components of cell wall are cellulose, hemicelluloses, pectic substances, lipid, proteins, etc. While primary wall is present at the beginning, secondary and tertiary walls develop later towards innerside of primary wall.