Cork is a type of protective tissue in plants, and it acts as a protective barrier to the external environment. It serves several important functions:
Protection against physical damage: The outer layer of cork cells, called the cork cambium or phellogen, produces cork cells filled with suberin, a waxy, waterproof substance. These cork cells are dead and form a protective outer layer on the plant’s stem, branches, and roots. This layer helps shield the plant from physical damage, such as abrasion, impact, and herbivore grazing.
Protection against water loss: Suberin in cork cells makes them impermeable to water and gases. This waterproof barrier prevents excessive water loss from the plant’s internal tissues and helps the plant retain moisture, especially in arid or dry conditions.
Protection against pathogens: Cork’s thick, durable structure and chemical composition also make it resistant to microbial attacks and pathogens. It forms a physical barrier that prevents the entry of fungi, bacteria, and other harmful microorganisms into the plant’s inner tissues.
Thermal insulation: Cork’s insulating properties help protect the plant from extreme temperature fluctuations. It acts as a thermal barrier, reducing the impact of temperature changes on the plant’s sensitive inner tissues.
Protection against fire: The suberin-rich cork cells also provide some protection against fire. Cork can resist burning, which can help prevent fires from spreading to the plant’s vital parts.
In summary, cork acts as a protective tissue by forming a robust, waterproof, and durable outer layer that shields the plant from physical damage, water loss, pathogens, temperature extremes, and even fire. This protective layer is essential for the survival and health of woody plants, such as trees and shrubs.