Cortex

Definition

The cortex is the outer layer of a plant's stem and roots, serving as a protective barrier and a site for storage and transport of nutrients. It plays a critical role in the plant's overall structure and function by supporting the vascular tissues and facilitating the movement of substances between the outer tissues and inner vascular system.

5 Must Know Facts For Your Next Test

1. The cortex is primarily composed of parenchyma cells, which have thin cell walls and are involved in storage, photosynthesis, and secretion.
2. In roots, the cortex often contains air spaces that facilitate gas exchange and help prevent suffocation in anaerobic conditions.
3. The cortex can also serve as a pathway for water and nutrients to move from the epidermis to the vascular tissues, playing a crucial role in overall plant health.
4. In some plants, the cortex may contain specialized structures, like aerenchyma, that allow for improved buoyancy and oxygen transport.
5. Cortex thickness can vary greatly among different plant species, influencing their adaptability to various environmental conditions.

Review Questions

• How does the structure of the cortex contribute to its function in both stems and roots?
  • The structure of the cortex, primarily made up of parenchyma cells, is crucial for its functions in both stems and roots. In stems, it supports vascular tissues while allowing for nutrient storage and transport. In roots, it not only serves as a storage area but also aids in water absorption and gas exchange due to its air spaces. This structural composition enables the cortex to effectively carry out its roles in maintaining plant health.
• Discuss how the presence of aerenchyma in the cortex can benefit certain plant species in wetland environments.
  • Aerenchyma in the cortex provides significant benefits to plant species adapted to wetland environments by enhancing buoyancy and facilitating gas exchange. This specialized tissue allows for air-filled spaces that enable oxygen to reach submerged roots, crucial for respiration. As a result, plants with aerenchyma can thrive in saturated soils where other plants may struggle due to low oxygen availability.
• Evaluate the role of the cortex in overall plant physiology, considering its interactions with other tissues such as xylem and phloem.
  • The cortex plays a vital role in overall plant physiology by acting as an intermediary between outer layers and internal vascular tissues like xylem and phloem. By facilitating nutrient storage and transport while regulating water movement, it ensures efficient resource distribution throughout the plant. Moreover, its interactions with surrounding tissues are essential for maintaining homeostasis, especially during stress conditions like drought or flooding. This interconnectedness highlights how crucial the cortex is to a plant's ability to adapt and survive in varying environments.

Related terms

Pith: The central part of the stem, composed of parenchyma cells, which stores nutrients and helps in the transport of water and minerals.

Endodermis: A specialized layer of cells surrounding the vascular tissue in roots, regulating the movement of water and nutrients into the vascular system.

Cambium: A layer of actively dividing cells between the xylem and phloem in stems and roots, responsible for secondary growth and the production of new vascular tissue.