The plant cell wall is a remarkable structure. It provides
the most significant difference between plant cells and other eukaryotic cells.
The cell wall is rigid (up to many micrometers in thickness) and gives plant
cells a very defined shape. While most cells have a outer membrane, none is
comparable in strength to the plant cell wall. The cell wall is the reason for
the difference between plant and animal cell functions. Because the plant has
evolved this rigid structure, they have lost the opportunity to develop
nervous systems, immune systems, and most importantly, mobility.
The cell wall is composed of cellulose fiber, polysaccharides, and
proteins. In new cells the cell wall is thin and not very rigid.
This allows the young cell to
grow. This first cell wall of these growing cells is called the primary cell
wall. When the cell is fully grown, it may retain its primary wall, sometimes
thickening it, or it may deposit new layers of a different material, called the
secondary cell wall.
On the whole, each cell's cell wall interacts with its neighbors to
form a tightly bound plant structure. Despite the rigidity of the cell
wall, chemical signals and cellular excretions are allowed to pass between
Diagram of a cell wall. The different layers of cell
wall are shown. The cell wall is composed of cellulose,
polysaccharides, and proteins.
Picture of Lily Parenchyma cell. The cell wall which
provides a rigid structure is in green.