You're on a roll — Here is the identification and labeling for the transverse sections of the dicot and monocot stems shown in the image.
Based on the arrangement of vascular bundles:
- The left diagram shows a Dicot Stem. Its vascular bundles are arranged in a distinct ring, and it has clear regions for cortex and pith.
- The right diagram shows a Monocot Stem. Its vascular bundles are scattered throughout the ground tissue, without a clear distinction between cortex and pith.
Here are the labels for each type of stem:
Dicot Stem (Left Diagram)
- Epidermis: The outermost protective layer, typically a single layer of cells.
- Cortex: Located just beneath the epidermis, extending to the vascular bundles. It consists of:
- Collenchyma: Often found directly under the epidermis, providing flexible support.
- Parenchyma: Ground tissue cells for storage.
- Sclerenchyma: May be present as a cap over the vascular bundles or in other supportive roles.
- Vascular Bundles: Arranged in a ring. Each bundle contains:
- Phloem: Located towards the outside of the stem, responsible for transporting sugars.
- Xylem: Located towards the inside of the stem, responsible for transporting water and minerals.
- Vascular Cambium: (Not explicitly visible at this magnification but present between xylem and phloem) Responsible for secondary growth.
- Pith: The central region of the stem, composed of parenchyma cells, primarily for storage.
- Medullary Rays: Parenchymatous cells located between the vascular bundles, connecting the cortex and pith.
Monocot Stem (Right Diagram)
- Epidermis: The outermost protective layer.
- Ground Tissue: The entire internal region of the stem, composed of parenchyma cells, where the vascular bundles are embedded. There is no distinct cortex or pith.
- Vascular Bundles: Scattered throughout the ground tissue. Each bundle is typically oval-shaped and surrounded by a sclerenchymatous bundle sheath for support. Each bundle contains:
- Phloem: Located towards the periphery of the bundle.
- Xylem: Typically V or Y-shaped, with larger metaxylem vessels and smaller protoxylem vessels, often with a protoxylem lacuna (air cavity).
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