The substance found in the cell wall of cork or bark that makes it impervious to water is suberin.

Suberin is a complex lipid polymer that is found in the cell walls of cork or bark tissues. It is a waxy and hydrophobic substance that acts as a barrier against water, gases, and pathogens. Suberin is responsible for the unique properties of cork, such as its impermeability to water and its ability to float.

Cork cells are dead at maturity and have thick walls that are impregnated with suberin. This layer of suberin makes the cork cells impermeable to water and prevents the loss or entry of water. The presence of suberin also makes the cork cells resistant to decay and microbial attack.

The role of suberin in preventing water loss is crucial for plants, especially those growing in arid or water-deficient environments. It helps the plants to conserve water by reducing transpiration through the bark or cork tissues. This is particularly important for trees and shrubs, as water loss through the bark can be significant.

The presence of suberin in the cell walls also provides mechanical support and protection to the underlying tissues. It makes the bark or cork tissues resistant to physical damage, such as abrasion or herbivory. Additionally, the hydrophobic nature of suberin prevents the entry of pathogens, such as fungi or bacteria, into the plant tissues.

In summary, suberin is the substance found in the cell wall of cork or bark that makes it impervious to water. It acts as a barrier against water loss, provides mechanical support, protects against physical damage, and prevents the entry of pathogens.

Suberlin