What is the Internal Structure of the Monocot Root Maize?

The internal structure of a maize (corn) monocot root exhibits distinct zones and tissues adapted for water and nutrient uptake.

Major Tissue Regions:

The maize root, like other monocot roots, is characterized by the following internal structures:

• Epidermis (Epiblema): The outermost layer, often with root hairs (unicellular extensions) to increase the surface area for water and mineral absorption.

• Cortex: A wide zone beneath the epidermis, composed primarily of parenchyma cells. These cells store starch and facilitate the radial transport of water and nutrients inward. Large intercellular spaces are present for aeration.

• Endodermis: A single layer of tightly packed cells surrounding the stele (vascular cylinder). The endodermis possesses Casparian strips, which are bands of suberin (a water-impermeable substance) embedded in the radial and transverse cell walls. These strips force water and dissolved minerals to enter the stele through the cytoplasm of the endodermal cells, allowing for selective uptake and preventing backflow.

• Stele (Vascular Cylinder): The central core of the root, containing the vascular tissues. Key features include:

  • Pith: A central region composed of parenchyma cells. This area stores food reserves, primarily starch grains, and facilitates the transfer of nutrients to other plant parts. The pith is made from thin-walled parenchyma tissue and contains intercellular spaces.
  • Vascular Bundles: Maize roots display radial vascular bundles, where xylem and phloem are arranged in alternating radii. Monocot roots like maize typically have numerous xylem and phloem strands. The bundles aren't separate but have vessels arranged in a V-shaped structure.
    • Xylem: Conducts water and minerals from the roots to the rest of the plant. Xylem vessels are located towards the center.
    • Phloem: Transports sugars (produced during photosynthesis) from the leaves to the roots and other parts of the plant. The phloem is situated between the xylem arms.
  • Conjunctive Tissue: Parenchyma cells located between the xylem and phloem bundles.
  • Pericycle: A single layer of cells located just inside the endodermis. It is the site of lateral root formation and contributes to the vascular cambium (if present).

Vascular Bundle Arrangement:

The vascular bundles in maize roots are radially arranged, meaning the xylem and phloem tissues alternate around the central axis. The number of xylem poles (protoxylem points) is typically high (polyarch condition).

Summary Table:

This structured arrangement ensures efficient water and nutrient uptake, transport, and storage, crucial for the plant's survival and growth.