Identify the positions of tissues as seen in transverse sections of non-woody dicotyledonous roots and stems, limited to: xylem, phloem and cortex

Sourav PanNovember 2, 2024

Answered

In the transverse sections of non-woody dicotyledonous roots and stems, the arrangement of tissues is distinct and organized. Below is an identification of the positions of the xylem, phloem, and cortex in these structures.

Transverse Section of Dicotyledonous Roots

1. Cortex:
   • Position: The cortex is located just beneath the epidermis and surrounds the vascular tissues.
   • Structure: It consists primarily of parenchyma cells, which are loosely arranged to allow for gas exchange and storage of nutrients.
2. Phloem:
   • Position: The phloem is situated towards the outer side of the vascular bundle, adjacent to the cortex.
   • Structure: In roots, phloem is typically found in smaller vascular bundles compared to stems. It consists of sieve tube elements and companion cells.
3. Xylem:
   • Position: The xylem is located towards the center of the vascular bundle, inside the phloem.
   • Structure: The xylem in roots usually has a star-shaped appearance in transverse sections and consists of tracheids and vessel elements that conduct water and minerals.

Transverse Section of Dicotyledonous Stems

1. Cortex:
   • Position: Similar to roots, the cortex is located just beneath the epidermis.
   • Structure: In stems, it can be divided into layers, including collenchyma (for support) and parenchyma (for storage).
2. Phloem:
   • Position: The phloem is located towards the outside of each vascular bundle, just beneath the cambium layer (if present).
   • Structure: The phloem in stems is typically larger than in roots and consists of sieve tubes, companion cells, and phloem parenchyma.
3. Xylem:
   • Position: The xylem is situated towards the center of each vascular bundle.
   • Structure: In stems, xylem vessels are often larger than those in roots and are arranged in a circular pattern around a central pith area. The xylem consists of vessel elements, tracheids, and fibers.

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