Periderm

Definition

Periderm is a protective tissue that replaces the epidermis in the stems and roots of many plants, particularly during secondary growth. It consists mainly of cork cells, which are dead at maturity and serve to insulate and protect the plant from environmental stressors such as water loss and pathogens. This tissue plays a crucial role in the overall structure and function of plant organs as they mature and expand.

5 Must Know Facts For Your Next Test

1. Periderm is formed during secondary growth and replaces the epidermis in older plant tissues, allowing for increased girth as the plant matures.
2. The cork cells in periderm are impregnated with suberin, a waxy substance that makes them waterproof and helps prevent water loss.
3. Unlike epidermal cells, which are alive when functional, cork cells are dead at maturity, providing structural support and durability to the plant's outer layers.
4. Periderm also includes lenticels, which facilitate gas exchange in woody plants, ensuring that internal tissues receive adequate oxygen.
5. The development of periderm is crucial for the survival of perennial plants, as it helps protect against environmental challenges throughout their lifespan.

Review Questions

• How does periderm contribute to a plant's ability to survive environmental stressors?
  • Periderm acts as a protective barrier for plants, insulating them from environmental stressors such as extreme temperatures, pathogens, and moisture loss. The cork cells within periderm are coated with suberin, which creates a waterproof barrier that helps prevent desiccation. This feature is especially important for woody plants that experience secondary growth, as it allows them to maintain their structural integrity while adapting to changing environmental conditions.
• Discuss the roles of cork cambium and cork in the formation of periderm.
  • Cork cambium is a key tissue responsible for generating cork cells that make up the periderm. As the plant undergoes secondary growth, the cork cambium divides to produce new layers of cork towards the outside, while also forming phelloderm towards the inside. The resulting cork provides protective qualities due to its dead cell structure and suberin content, which helps insulate the plant and prevent water loss. Together, these components ensure that periderm effectively serves its protective function.
• Evaluate how the presence of lenticels within the periderm impacts a plant's physiology.
  • Lenticels play a crucial role in a plant's physiology by facilitating gas exchange between internal tissues and the external environment. Located within the periderm, these small openings allow oxygen to enter and carbon dioxide to exit, supporting cellular respiration even in structures covered by protective layers. This exchange is vital for sustaining metabolic processes in woody plants, especially during periods of active growth or when stomata are closed due to drought or other stressors. Thus, lenticels contribute significantly to a plant's ability to maintain homeostasis while being shielded by periderm.

Related terms

Cork Cambium: A lateral meristematic tissue responsible for producing cork cells, which contribute to the formation of the periderm.

Cork: The outermost layer of the periderm, made up of dead cells that provide insulation and protection to the underlying tissues.

Lenticels: Small openings in the periderm that allow for gas exchange between the internal tissues of the plant and the atmosphere.