The cells of all plants, bacteria and fungi have a rigid, protective covering outside the plasma membrane called cell wall. The presence of cell wall in plant cells distinguishes them from animal cells. Among the vascular plants only certain cells connected with the reproductive processes, are naked, all other cells have walls. The cell wall was first observed by Hooke in the year 1865 in cork cells. Originally it was thought that the cell wall was a non-living secretion of the protoplasm, but now it is known to be metabolically active and is capable of growth and at least during its growth, contains protoplasmic material.
Formation of the cell wall
During the telophasic stage of mitosis, the phragmoplast widens and becomes barrel shaped. At the same time, on the equatorial plane the cell plate i.e the first evident partition between the daughter protoplasts, begins to form inside the phragmoplast. In the area where the cell plate forms, the fibres of the phragmoplast become indistinct and are restricted to the circumference of the cell plate. When the cell plate is completely formed the phargmoplast disappears completely. At this stage thin lamellae are laid down by the daughter protoplasts on both the sides of the cell plate. The cell plate gradually undergoes changes to form the intercellular substances referred to as the middle lamella.