peridermiksen

Peridermiksen is a term that refers to the outermost layer of cells in a plant's stem and root, specifically the secondary protective tissue that replaces the epidermis as the plant undergoes secondary growth. This tissue is crucial for providing structural support and protection against mechanical injury, desiccation, and pathogen invasion.

The periderm is composed of three distinct layers. The outermost layer is the cork, also known as phellem, which consists of dead cells with suberized cell walls. Suberin is a waxy substance that makes the cork waterproof and impermeable to gases. Beneath the cork lies the cork cambium, or phellogen, a layer of actively dividing cells responsible for producing the cork cells outwards and the phelloderm inwards. The innermost layer is the phelloderm, which is composed of living parenchyma cells.

In woody plants, the periderm forms as the stem or root increases in diameter. The original epidermis, being a primary tissue, cannot expand sufficiently and is eventually sloughed off. The cork cambium arises in the outer cortex or epidermis and produces the new protective layer. The periderm is often punctuated by lenticels, which are small, porous areas that allow for gas exchange between the internal tissues and the atmosphere. The thickness and composition of the periderm can vary significantly between different plant species and even on different parts of the same plant, reflecting adaptations to diverse environmental conditions.