What are medullary rays and what are their functions?

Medullary Rays

• Definition: Medullary rays are radial sheets or bands of parenchyma cells found in between the vascular bundles of a stem or root.
• They extend from the center (pith) towards the periphery (cortex) of the plant organ.
• They are a characteristic feature of dicot stems and roots, seen clearly in a transverse section (T.S.) of wood.

Functions of Medullary Rays

1. Lateral Transport: They help in the sideways conduction of water, minerals, and food between the xylem and phloem.
2. Storage: The parenchyma cells in medullary rays store food materials and sometimes water.
3. Strength & Support: They provide radial support to the plant structure.
4. Secondary Growth: During secondary growth, medullary rays help in the movement of substances between newly formed vascular tissues.