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Definition

noun

A thick layer rich in lignin that strengthens and waterproofs the wall and is formed inside the primary cell wall that has stopped increasing in surface area when the cell is fully grown.

Supplement

When the cell stops from expanding, a secondary wall is deposited between the primary cell wall and plasma membrane that renders support, strength and protection.

The secondary cell wall consists mainly of cellulose, but also other polysaccharides, lignin and proteins. In some cells, such as found in xylem, the secondary cell wall contains lignin, which strengthens and waterproofs the wall. Other plant cells have secondary cell wall with additional function, such as food storage. For example, cotyledons and endosperm have secondary cell walls that contain little cellulose but more on polysaccharides.

Compare: primary cell wall, middle lamella.
See also: cell wall.