Each of the following terms has some anatomical significance. What do these terms mean? Explain with the help of line diagrams.

a. Plasmodesmata

b. Middle lamella

c. Secondary wall

a. Plasmodesmata – A microscopic channels between two cells through the cell wall are called Plasmodesmata. Plasmodesmata allow transport of materials between two cells. They are protoplasmic strands between adjacent plant cells.

b. Middle lamella – It is a layer in the cell wall and is made of calcium pectate (mainly) and magnesium pectate. It helps in cementing between two neighbouring cells. During ripening a fruit becomes soft and pulpy due to dissolution of middle lamella.

c. Secondary wall – this is a non-extensible layer. It is made of hemicelluloses. It provides rigidity to the cell. The cell wall of a young plant cell is capable of growth, which gradually diminishes as the cell matures and the secondary wall is formed on the inner (towards membrane) side of the cell. Secondary cell wall may have the deposition of lignin. Secondary wall helps in the differentiation of the cell.