Root: Types, Modification and Functions | Plant Morphology

In this article, we will discuss about:- 1.General Characteristics of Root 2. Types of Roots 3. Modifications of Roots and 4. Functions of Root

1.General Characteristics of Root:

• Root is the descending or underground part of the plant axis.

• Root is usually positively geotropic (i.e. grows downward into the soil) and positively hydrotropic (i.e. grows towards the source of water) but negatively phototropic (i.e. grows away from sunlight).

• Root is usually cylindrical and non-green (i.e. lack chlorophylls), but sometimes green as in Trapa and Taeniophylum.

• Root does not bear nodes, internodes, leaves or buds (exceptions are sweet potato, wood apple etc.)

• The growing point of root tip is sub-terminal and protected by a root cap or calyptra.

• Unicellular root hairs present just behind the root caps which increase the absorptive surface area of roots,

• Lateral roots are endogenous in origin i.e. arise from pericycle of the main root.

2. Types of Roots:

(a) Tap root
(b) Adventitious root

3. Modifications of Roots:

Roots are modified into different forms to perform specific functions other than their normal functions. Modification in roots is found in both tap root system and adventitious root system.

Modification in root occurs when there occurs a permanent change in the structure of the root system. This change in structure of the tap root or the adventitious root system is for carry out certain specific functions additional to anchorage and absorption. The change in the structure of the roots is for adaptation to their surrounding environment.

A) Tap Root Modifications:

Tap roots are modified in to different structures, these modified structures carry out specific functions like food storage. Such roots are referred to as modified tap roots. They are different types of modified tap roots like Fusiform, Napiform and Conical

Fusiform: Fusiform is a modified tap root. The primary root of the system is swollen at the middle and tapers gradually at both the ends forming a spindle shaped structure. Example of fusiform roots is radish.

Napiform : The base region of the root is swollen becoming almost spherical in shape, and then it abruptly tapers towards the lower end, forming a tail-like structure. Example of Napiform roots are turnip and beet.

Conical: In the conical form of root modification the roots are swollen and are broad at the base, the apex part gradually tapers forming a con like structure like in carrot.

B) Adventitious Root Modifications:

Adventitious roots are the roots that are produced from any portion of the plant other than the radicle. The root system may be changed to different forms for special functions like storage, Respiration, mechanical support and vital functions. 

i) For Storage Of Food

Tuberous root: The adventitious roots in this are grown from the nodes of the running stem. These roots are modified are swollen into irregular forms and are known as tuberous roots. They are produced in single number. Example: Sweet Potato.

Fasciculate root: The tuberous roots are developed from the base of the stem in cluster. 

Nodulose root: The adventitious roots in this case arise from the underground stem. Some roots that are  slender become swollen near the apex and they form nodule like structures. Example: mango-ginger.

ii) For Mechanical Support

Prop roots : Here the plants have tap roots system. the horizontal branches of the stem of the plant gives rise to aerial roots. These aerial roots hang vertically downwards. These roots on reaching the ground, they grow and act like pillars. They provide mechanical support to the plant. Example Ficus bengalensis.

Stilt Roots : These plants have their own roots system like in screwpine. They are not strongly anchored tothe soil. Hence, these plant develop adventitious roots from near the base of the stem. These roots grow obliquely downwards. They act like stilt and they provide mechanical support to the plant. Example - the maize plant produces adventitious roots form the lower nodes which also act in a similar way. 

Climbing roots : This type of root system is found in climbers. Adventitious roots are developed from the nodes and are aerial roots. These aerial roots twist and clasp the support and help in climbing. Example Betel, Pothos, etc. 

Clinging roots : This type of roots are seen in orchids. These roots arise from the stem base of the plant. They enter crevices of the support to fix the epiphyte. They provide the plant with mechanical support. 

Root buttresses : Some trees have great plant-like roots that radiate from the base of the stem of the tree. It consists of partly root and partly stem. Example is Bombax.

iii) For Mechanical Support:

Pneumatophores : The pneumatophore roots grow vertically up, they protrude out of water or marshy sol like conical spikes. These roots occur in large number around the trunk of the tree. Pneumatophore roots are many pores for breathing through which exchange of gases takes place for respiration. Example of pneumatophores are Rhizophora. 

iv) For Vital Functions:

Sucking roots or Haustoria : Cuscuta is a leafless, parasitic plant, it always grows in association with other plants. The parasatic plant at the point of attachment with the host plant produces some knob like roots known as haustoria which penetrate into the host plant and draws nourishment. 

Epiphytic roots : are the plants like orchids that grow perched on tree branches. They attach themselves firmly to the trunk of the tree by the aid of social roots known as climbing roots.  They also have aerial roots for absorbtion. These roots are fleshy and remain along with the clinging roots. These roots have spongy tissues which absorb moisture from the atmosphere. They also have chlorophyll pigment and photosynthesis takes place. 

Floating roots:  are found in aquatic plants. These roots develop from the nodes of the floating branches. The roots are spongy and are colorless. These roots are present above the level of water. As these roots are spongy and soft, they store air in them which help the plant in floating. They also help in respiration process. 


Assimilatory roots: are normally non-green in color. The adventitious roots are developed from the branches of the plant Tinospora cord folia. These branches are green in color and carry out photosynthesis, the roots developed from this are known as assimilatory roots. The assimilatory roots are slender, long and in hanging state.

4. Functions of Root:

• Its main functions are the absorption of water the and minerals from the soil.
• It provides a proper anchorage to the plant parts.
• it transport absorbed water and minerals to the stem through the xylem.
• Storing reserve food material and synthesis of plant growth regulators are its other functions.
• By undergoing medications in their structure, roots perform special physiological
• functions like food storage, assimilation, absorption of atmospheric moisture, sucking food from the host, better gaseous exchange and mechanical functions like floating (buoyancy), stronger anchorage and climbing