AP BIOLOGY

Detailed explanation-1: -Collenchyma. Cells are long and thick-walled. The cell wall is made up of cellulose and pectin.

Detailed explanation-2: -Sclerenchyma tissue, when mature, is composed of dead cells that have heavily thickened walls containing lignin and a high cellulose content (60%–80%), and serves the function of providing structural support in plants. Sclerenchyma cells possess two types of cell walls: primary and secondary walls.

Detailed explanation-3: -The xylem has a thick cell wall which has the deposition of the water-impermeable substance (lignin) whereas the phloem has a thin cell wall and made up of cellulose.

Detailed explanation-4: -Both lignin and cellulose are found in the rigid cell walls of the xylem cells (those that conduct water) in the primitive plant Selaginella.

Detailed explanation-5: -Xylem contains dead cells which are formed of thick cell walls and a high content of lignin. The reason for the thick cell walls is to provide less resistant to the flow of the solution mainly the water and other dissolved nutrients.