Peridermes

Peridermes refers to the collective term for the secondary dermal tissues of plants, primarily functioning as a protective outer layer that replaces the epidermis in woody plants and some herbaceous species. It is a complex tissue that develops from the cork cambium, also known as the phellogen. The periderm is generally composed of three layers: the phellem (cork), the phellogen (cork cambium), and the phelloderm.

The phellem, or cork, is the outermost layer and consists of dead cells with suberized cell walls, making it waterproof and resistant to mechanical injury and pathogen invasion. The cork cambium is a meristematic layer responsible for producing new cells outwards to form phellem and inwards to form phelloderm. The phelloderm, the innermost layer, is composed of parenchyma cells and plays a role in storage and nutrient transport.

Periderms are essential for the survival of woody stems and roots, providing insulation against extreme temperatures and preventing desiccation. In many plants, the periderm is interrupted by lenticels, which are small pores that allow for gas exchange between the internal tissues and the atmosphere. The development and structure of periderm can vary significantly between plant species, reflecting adaptations to different environmental conditions. It is a dynamic tissue that undergoes continuous formation and differentiation throughout the plant's life.