Botany - Cell - The Unit of Life Question with Solution | TestHub

In mature cells, more layers of wall material are added internal to the primary wall and they are called a secondary wall. Growth by the addition of new wall material on the primary wall is called accretion. It has more cellulose and less hemicellulose. The secondary wall is thick and rigid. It usually consists of three layers, which are often named S1, S2 and S3 It is found in collenchyma and sclerenchyma cells, xylem vessels. The secondary cell wall grows by apposition. In this method, new cell wall material secreted by protoplasm is deposited as definite thin plates one after the other on the inner surface of the original wall.