Respuesta :
The secondary cell wall is a structure found in many plant cells, located between the primary cell wall and the plasma membrane. The cell starts producing the secondary cell wall after the primary cell wall is complete and the cell has stopped expanding.
Secondary cell walls provide additional protection to cells and rigidity and strength to the larger plant. These walls are constructed of layered sheaths of cellulose microfibrils, wherein the fibers are in parallel within each layer. The inclusion of lignin makes the secondary cell wall less flexible and less permeable to water than the primary cell wall. In addition to making the walls more resistant to degradation, the hydrophobic nature of lignin within these tissues is essential for containing water within the vascular tissues that carry it throughout the plant.
The secondary cell wall consists primarily of cellulose, along with other polysaccharides, lignin, and glycoprotein. It sometimes consists of three distinct layers - S1, S2 and S3 - where the direction of the cellulose microfibrils differs between the layers.
Answer:
The secondary wall form on the outer surface of the primary wall due to presence of middle lamella.
Explanation:
Middle lamella is present between the primary walls of the adjacent plant cells. Middle lamella is a sticky layer that serves to cement the adjacent plant cells together.
Due to the presence of stick middle lamella towards the outer side of the primary cell wall, the deposition of material to form the secondary cell wall occurs towards the inner side of the primary cell wall only.
