The Primary Cell Wall

The cells of plants are normally enclosed by either a more or less rigid cell wall containing cellulose. Only some protists and a few algae and endosperm cells do not have cell wall. Some groups of algal contain other structural substances than cellulose.

Primary Cell Wall Structure

 The basic structure of cell walls are usually compared to that of reinforced concrete: cellulose in plants, the scaffolding substance, and iron in concrete is rooted in an amorphous ground substance, the matrix.

The main primary cell wall functions include giving cells stability; determining their shape; protects the cell against bacteria, viruses, fungi and other pathogens; influences the development of the cells; and counter balances the osmotic pressure. The cell wall of elongating cells is still elastic, a property that is lost in fully differentiated cells. It is therefore distinguished between a primary and a secondary wall.

Primary Cell Wall Development

The primary cell wall normally develops between the two daughter cells during early telophase and is laid out during the first division of the cell. The early stage of new cell is the cell plate, which is a lamella-like structure in the former equatorial plane of the mitotic apparatus. Studies have shown that it develops by fusion of several vesicles wherein the electron dense material is deposited at both sides. Phragmoplast is the developed structure and the immediate precursor of the primary wall.

Since the primary cell wall is created during cell division, it is normally flexible and thin at first, so that it can accommodate the elongation and enlargement of cells. When the cell matures, it is strengthened and stops growing. The secondary wall, on the other hand, is normally present between the primary cell wall and the plasma membrane in some cells. The secondary cell wall is deposited in various laminated layers and is durable and strong. It provides both cell support and protection.

©2005-2015 Plant Biology Advice - Dean Ravenscroft