Suberin
Explanation
Cork cells are mature, dead cells found in the outer protective layer (bark) of woody plants. To perform their protective function effectively, the cell walls of cork undergo a specific chemical modification that acts as a barrier against environmental factors.
Option Analysis
- Lignin is incorrect: Lignin is a complex organic polymer deposited in the cell walls of sclerenchyma tissues (such as wood fibers). It provides mechanical strength, rigidity, and structural support to the plant, but it is not the primary substance responsible for the impermeability of cork.
- Suberin is correct: Suberin is a waxy, lipophilic substance deposited in the cell walls of cork cells. This deposition (suberization) makes the walls impervious to water and gases, preventing desiccation and protecting the underlying tissues from infection and physical damage.
- Cutin is incorrect: Cutin is a waxy polymer that forms the cuticle on the outer surface of the epidermal cells of leaves and young stems. Its primary function is to reduce water loss through transpiration, but it is distinct from the suberin found in cork.
- Cellulose is incorrect: Cellulose is the fundamental structural polysaccharide present in the primary cell walls of all plants. While it provides tensile strength, cellulose itself is permeable to water and solutes.
Key Takeaway: Suberin is the specific waxy chemical substance deposited in the walls of cork cells that renders them impervious to both water and gases.