Plant Cell Walls

Cell Wall Structure

• The cell wall has three fundamental parts: middle lamella, primary wall, and secondary wall.

Middle Lamella

• The middle lamella cements together the walls of neighboring cells.
• It is typically thin, with a thickness of around 1 µm.
• In woody tissues, the middle lamella is commonly lignified.

Primary Wall

• The primary wall is the first wall formed in a developing cell.
• It has a thickness of around 1-3 µm.
• The primary wall is more or less elastic and extendable, crystalline, and optically active.
• It is composed of cellulose, pectic compounds (mainly polysaccharides), and hemicellulose.

Secondary Wall

• The secondary wall follows the primary wall in development.
• It is laid down inside the primary wall.
• The secondary wall has a thickness of around 5-10 µm.
• It is more or less rigid, crystalline, and strongly optically active.
• It is mainly composed of lignin, cellulose, non-cellulosic polysaccharides, hemicelluloses, and mineral salts of Ca, Mg, K, and some silica.

Cell Wall Function

• The main role of the cell wall is to form a framework for the cell and prevent over-expansion.
• Cellulose fibers, structural proteins, and other polysaccharides help maintain the shape and form of the cell.

This quiz covers the structure and composition of plant cell walls, including the middle lamella, primary wall, and secondary wall.