Final answer:
The periderm serves as a protective layer for woody plants, composed of the cork cambium, cork cells, and phelloderm. It is essential for water retention, protection against physical damage and pathogens, and it enables gas exchange through specialized structures called lenticels.
Step-by-step explanation:
The periderm is the outermost covering of woody stems and roots, serving as a protective tissue in mature plants. It effectively replaces the epidermis, the plant’s primary protective layer during early growth stages. The periderm is composed of the cork cambium, cork cells, and the phelloderm. Cork cells, developed by the cork cambium, contain a waxy substance known as suberin, which is water-repellent, aiding in reducing water loss from the plant body.
Moreover, the periderm serves multiple protective functions against physical damage and pathogens. It acts as an effective barrier, making it difficult for organisms to infiltrate plant tissues and helps in water retention. In some plants, the periderm features lenticels, which are openings that allow for the exchange of gases, ensuring that even as the outermost layer, the plant can still facilitate respiration through its cortex and vascular tissues.
The combination of the cork cambium, cork cells, and phelloderm, which collectively make up the periderm, is crucial for the longevity and health of woody plants. The ability to protect the plant, conserve water, and facilitate controlled gas exchange underscores the significance of the periderm as a protective and functional layer in plant biology.