Root System– Definition, Types, Functions and Examples

The roots are modified organs found in vascular plants that transport water and nutrients to the plant body, allowing the plants to grow taller more quickly. Roots are normally an underground part of a plant, but sometimes they grow above the ground.

Some plants like mosses and liverworts do not have roots. The plant body is mainly composed of the shoot and root systems. Let’s go through this article to learn more about roots. Roots help provide food, nutrition, soil integrity (by preventing erosion). Let’s learn the root system how they help plants grow in the article.

Learn about Leaf in Plants here

Root Definition

The root is the non-green, underground or descending, positively geotropic, negatively phototropic, positively hydrotropic, and endogenous part of the plant body. It develops from the radicle of the embryo. 

Characteristics of the Root

The characteristics of the root are mentioned below:

• The root is the underground descending portion of the plant axis.
• The roots are non-green due to the absence of chlorophyll pigments. The roots of Trapa and Tinospora show photosynthesis.
• The root generally develops from the radicle of the embryo.
• Roots do not have nodes and internodes.
• Roots do not bear leaves, buds, or reproductive organs. The roots of Trichosanthes bear buds for vegetative propagation.
• The root parts are the primary root, lateral roots, the apical meristem, root cap, and root hairs.
• A root cap protects the root apex.
• Unicellular hairs are present a little behind the apex of the root.

Types of Roots

The roots are divided into three types which are:

• Taproot
• Fibrous root
• Adventitious root

1. Taproot: The seed’s radicle elongates and grows to form the primary root. The lateral branches of the primary root are called secondary roots. The secondary roots, in turn, branch to form tertiary roots, e.g., dicotyledonous roots. The primary root, with its lateral branches, forms the taproot system. Taproots can penetrate deep into the soil. Example: Pea, gram, carrot, mustard plant, etc.

2. Fibrous root: In monocotyledonous plants, the primary root is short-lived and replaced by many roots. These roots originate from the stem base and constitute the fibrous root system. These roots do not penetrate deep into the soil. Example: Maize, sugarcane, wheat plant, etc.

3. Adventitious root: In this, the radicle dies immediately after germination. Hence these roots arise from different plant portions other than the radicle and are called adventitious roots. Example: Banyan tree, Monstera, etc.

Fig: Types of Roots

Regions of the Root

A root is differentiated into four regions:

1. Root cap: 

• i. A thickened, protective cap-like structure is present at the root apex.  
• ii. The root cap cells secrete mucilage (mucus), which lubricates the passage of the root through the hard soil. 
• iii. In some aquatic plants, the root pockets are present.

2. Meristematic region: 

• i. It is situated behind the root cap.  
• ii. This region is made up of actively dividing meristematic cells, which are responsible for the longitudinal growth of the root.

3. Region of cell elongation: 

• i. It is present just above the meristematic zone.
• ii. The cells of this region elongate rapidly and bring about an increase in the length of the root.  
• iii. These cells undergo differentiation.  

4. Region of maturation: 

• i. Cells from the elongation zone gradually differentiate and mature.
• ii. Root hairs are very fine and delicate, and thread-like structures formed from some of the epidermal cells of this region. 
• iii. These root hairs can absorb water and minerals from the soil.

Fig: Regions of the Root

Modifications of Roots

Roots may be modified to perform special functions like storage of food, support, and respiration apart from the normal functions. These modifications are found both in tap and adventitious roots.

(i) Taproot:

(a) Conical Root: When the root is swollen at the base and gradually tapers towards the apex, it is said to be conical.

Example: Carrot (Daucus carota).

(b) Fusiform Root: The primary root is swollen in the middle while both the ends gradually taper towards the apex and base; it is said to be fusiform.

Example: Radish (Raphanus sativus).

(c) Napiform Root: When the root is considerably swollen at the base and suddenly tapers towards the apex, it is said to be napiform.

Example: Beetroot (Beta vulgaris).

(d) Pneumatophores are also called respiratory roots and are found in mangrove plants, which grow in saline swamps near the seashore. Pneumatophores are negatively geotropic; they arise from the underground roots and grow vertically upwards, projecting several inches above the soil surface.

Example: Avicenna.

Fig: Modifications of Taproot

(ii) Adventitious root:

(1) For Storage of Food: 

(a) Tuberous Roots: These adventitious roots are swollen without any definite shape. They are produced singly and not in clusters. The tuberous roots of this plant also bear adventitious buds and behave as reproductive roots. 
Example: Sweet potato (Ipomoea batatas).
(b) Fasciculated Roots: These roots are in the form of a cluster at the base of the stem.
Example: Dahlia, Asparagus. 
(c) Moniliform or Beaded Roots: Roots have a beaded or moniliform appearance. They are swollen at frequent intervals.
Example: Momordica.
(d) Nodulose Roots: Roots are slender and suddenly become swollen near the tips and form nodules like structures. 
Example: Ginger (Zingiber officinale).
(e) Annulated Roots: Roots have a series of ring-like swellings.
Example: Ipecac (Carapichea ipecacuanha).

Fig: Adventitious Root Modifications for Storage of Food

(2) For mechanical support:

(a) Prop roots: These roots arise from the horizontal branches of the stem and grow vertically downwards in the soil. They become thick, pillar-like, and provide mechanical support to the giant trees.
Example: Banyan tree (Ficus benghalensis).
(b) Stilt roots: These are small, thick, and supporting roots growing obliquely from the lower nodes of the stem. Like prop roots, they also provide mechanical support.
Example: Maize (Zea mays), Sugarcane (Saccharum officinarum).
(c) Climbing roots: These roots may arise from the nodes of many climbers. They help the plant to attach themselves to support.
Example: Tongavine (Epipremnum pinnatum).
(d) Buttress roots:  These roots arise from the basal part of the main stem.
Example: Bombax.

Fig: Adventitious Root Modifications for Mechanical Support

(3) For Vital functions:

(a) Floating Roots: In some floating aquatic plants, white, spongy, and inflated roots arise from the nodes. They project above the water level. These roots have numerous air spaces. Therefore, they help in maintaining buoyancy and facilitate respiration.
Example: Jussiaea.
(b) Parasitic or Sucking Roots or Haustoria: Parasitic plants develop some aerial roots, penetrating the host tissues to absorb the nourishment. At the point of attachment with the host plant, it produces some knob-like roots known as haustoria. These roots come in contact with the xylem and phloem of the host through which water and food are supplied to the parasite.
Example: Cuscuta.
(c) Assimilatory or Photosynthetic Roots: Aerial adventitious roots of some plants develop chlorophyll and become assimilatory in function, i.e., they synthesize food.
Example: Tinospora and Water Chestnut (Trapa).
(d) Epiphytic Roots: Roots hangly in the air. They are hygroscopic, i.e. help in the absorption and storage of water by a special tissue called velamen.
Example: Orchids.

 Fig: Adventitious Root Modifications for Vital functions

Functions of Roots

The Primary and Secondary functions of roots are as follows:

 A. Primary functions:

(i) Roots help in the fixation and absorption of water and minerals from the soil.
(ii) Roots help in the upward movement of the absorbed water and minerals into the stem.
(iii) Roots penetrate the soil and provide support to plants.

B. Secondary functions:

(i) Roots of many plants store food.
(ii) Some roots are green and photosynthetic, like the roots of Tinospora and Trapa.
(iii) Some roots help parasitic plants to penetrate the hosts for the absorption of food like Cuscuta.
(iv) Some roots are respiratory and help plants in the exchange of gases like Avicenna.
(v) Some roots show symbiotic association with nitrogen-fixing bacteria.

Summary

The root is the non-green, underground part of the plant body. It develops from the radicle of the embryo. The roots are divided into taproot, fibrous root, and adventitious root. The different root regions are root cap, meristematic region, region of cell elongation, and region of maturation. Roots help in the soil’s fixation and absorption of water and minerals. Roots may be modified to different shapes to perform special functions like food storage, support, and respiration apart from the normal functions.

FAQs

Q.1. What are roots?
Ans: The roots are the underground organ found in vascular plants that helps to absorb water and mineral nutrients from the soil.

Q.2. Where are root hairs present in the root?
Ans: The root bears unicellular root hairs in the zone of maturation.

Q.3. Mention the types of roots.
Ans: The main types of roots are taproot, fibrous root, and adventitious root.

Q.4. Write the difference between taproot and fibrous root?
Ans: The difference between taproot and fibrous roots are:
1. Taproot are found in dicots, whereas fibrous roots are present in monocots.
2. Taproot develops from the radicle, whereas fibrous root develops from the stem or leaves.

Q.5. Mention some edible roots.
Ans: Some edible roots are: ginger, turnip, beet, carrot, etc.

Learn about the aerial shoot system here

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