Diagram the internal structure of a dicot stem after primary...

Name: Problem 6, Chapter 44: Biology: Life on Earth with Physiology
Uploaded: 2022-03-06T06:15:41-08:00
Channel: Elise Morgan
Description: Diagram the internal structure of a dicot stem after primary growth, labeling and describing the function of the epidermis, cortex, pith, xylem, and phloem. How does the structure change after secondary growth?

Diagram the internal structure of a dicot stem after primary growth, labeling and describing the function of the epidermis, cortex, pith, xylem, and phloem. How does the structure change after secondary growth?

Key Concepts

Phloem

Phloem is the vascular tissue that transports organic nutrients, particularly sugars produced during photosynthesis, throughout the plant. In dicot stems, phloem is typically located toward the exterior of the vascular bundle relative to the xylem and works in tandem with xylem to maintain the plant's nourishment and energy distribution.

Pith

The pith is found at the center of the stem, consisting of loosely arranged parenchyma cells. Its roles include storage of nutrients and water, and it may also facilitate the internal transport of substances. The pith can serve as a reservoir that supports the metabolic needs of the stem and surrounding tissues.

Xylem

Xylem is the vascular tissue responsible for the upward transport of water and dissolved minerals from the roots to other parts of the plant. In a dicot stem, xylem is often arranged internally relative to the phloem and becomes reinforced during secondary growth to contribute to the wood of the plant.

Cortex

Located just beneath the epidermis, the cortex is composed primarily of parenchymal cells that serve as sites for photosynthesis, storage of nutrients, and sometimes mechanical support. This tissue acts as an intermediary region between the protective outer layer and the vascular tissues.

Dicot Stem Anatomy

This concept encompasses the structural organization of a dicotyledonous stem, particularly focusing on the arrangement of different tissues after primary growth. It involves the outer epidermal layer, a cortex region, a central pith, and a vascular bundle system that includes xylem and phloem, arranged in a specific developmental pattern that supports functions like protection, storage, and transport.

Secondary Growth

Secondary growth involves an increase in the stem's girth rather than its length, and it is facilitated by the activity of lateral meristems such as the vascular cambium. In dicots, secondary growth leads to the production of additional xylem (wood) and phloem, and sometimes a cork layer (from the cork cambium) replacing the epidermis, thereby reinforcing the stem's structural integrity and enhancing its transport capacity.

Primary Growth

Primary growth refers to the elongation of the plant stem due to cell division in the apical meristems. In dicot stems, this growth results in the initial differentiation of tissues into the epidermis, cortex, pith, and vascular tissues (xylem and phloem) arranged in a specific configuration that supports basic plant functions during early development.

Epidermis

The epidermis is the outermost cellular layer of the stem that provides a protective barrier against physical injury, pathogenic organisms, and water loss. It plays a crucial role in the plant's overall defense system and helps mediate interactions with the external environment.

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