Dicot vs Monocot Roots
Angiosperms or flowering plants can be classified into two major classes, depending on their different morphological characteristic features; namely, Dicots and Monocots. Both these types have the same basic structure of plants, including stem, leaves, roots, and flowers, but they differ in their morphology. Roots mainly serve as the primary water and mineral absorbing organs in plants. They also act to anchor the plant in the soil, and may serve as storage organs and vegetative reproduction structures in certain plant species. Dicots and gymnosperms usually have a persistent taproot, which exhibits secondary growth, whereas monocots have a taproot, which is ephemeral and is replaced with a fibrous root system with many adventitious roots. Generally, primary roots of both groups are in the range of 0.04 to 1 mm in diameter, but monocots often have smaller roots than dicots.
Epiblema of dicot root is characteristically single layered, comprising tubular living components. The cuticle is absent on the epidermis. Root hairs can be found on the outer cell layer of the epidermis. The cortex of monocot root is uniform and is composed of thin-walled parenchyma cell layers with conspicuous intercellular spaces. Endodermis is the innermost layer of cortex that completely surrounds the stele. The transverse and radial walls of endodermis cells contain a band of lignin and suberin, called Casparian strip, which makes these cells unique from the rest of root cells. The casparian strip controls the movement of materials from cortex to stele. Stele is considered as the tissue inside the endodermis. It includes pericycle, vascular bundles and pith. Pericycle is the originating point of lateral roots and is composed of thick-walled parenchymatous cells. Vascular bundles are radial, and it contains xylem and phloem tissues. Pith is usually small, or it is absent in dicot roots.
Epiblema is more or less similar to that of dicot roots. Cortex of monocot is smaller and have characteristic casparian strip in the epidermis like in the epidermis of dicot. Certain endodermal cells called ‘passage cells’ are used to transfer water and dissolved salts from cortex directly into the xylem. Like in the dicot root, the stele of monocot is composed of pericycle, vascular bundles and pith. Unlike in the dicot root, monocot root has well developed pith.
What is the difference between Monocot and Dicot Roots?
• Vascular bundles in dicot root vary from 2 – 4 and rarely 6, whereas that of monocot root are numerous (8 or more bundles).
• In dicot root, cambium appears as secondary meristem at the time of secondary growth whereas, in monocot root, cambium is absent.
• Xylem vessels in dicot root are smaller in size and are polygonal in shape while, in monocot, these are large and more or less circular in outline.
• Dicot root undergoes secondary phase, whereas monocot root does not.
• Pith in monocot root is large while it is very small or absent in dicot root.
• Monocot roots, usually, are fibrous, while dicot roots are usually taproots.
• The primary roots of monocots are smaller in diameter than that of dicots.
• Unlike in monocot roots, the xylem plates usually extend into the center, to form a solid central core without any pith in dicot roots.
• The cortex of monocot root is smaller than that of dicot root.