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Modification of roots |
So, in this article we will discuss about the Modification of roots in details such as Types of roots, Modifications of Tap root and Modifications of Adventitious root etc.
Definition of Root:
The root is non-green, underground, cylindrical, descending axis of the plant body i.e. positively geotropic. It develops from the radical produces endogenous lateral branches and does not possess nodes, internodes, leaves and buds.
Functions of root:
The root normally performs the following functions:
1) To fix or anchor the plant to the soil.
2) To absorb water and minerals from the soil.
Root System:
There are two types of root systems present in plants:
1) Tap root system:
A root that develops from the radical of an embryo during seed germination is called a true or tap root. The tap root continues to grow and bear branches on it. The main root is called primary root. Its branches of first order are called secondary roots, and branches of second order are tertiary root and so on.
The main root along with its branches, form a tap root system. The branches are at the base and youngest toward the tip. The tap root system is usually present in dicotyledonous plant.
Examples: Sunflower, Mango etc.
2) Adventitious root system:
The roots which develop from any plant part other than radical are called adventitious roots and adventitious root along with their branches together constitious roots system.. This root system does not develop from radical because during seed germination radical grows into primary root for a while and dies and then the root system develops from base of the stem.
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Aventitious root system |
They are slender and fibre-like and hence the adventitious root system is also known as Fibrous root system. Adventitious root system is seen in Monocotyledonous plant.
Examples: Maize, Rice, Grasses etc.
Modifications of Root:
When the root or any other organ of a plant is doing some other functions than the normal one, it gets changed in form. Such changed forms are called modifications. Some of the modifications of root are described below:
A) Modifications of the tap root:
1) For Food Storage:
In some plants, underground primary tap storage of food. The secondary roots remain thin. In these cases, the stem is very much reduced to form a disc and leaves arisin . Mg from this reduced stem, are called radical leaves. The swollen tap root acquires some typical shape and is accordingly classified the following three types.
a) Fusiform Root:
The storage root which is swollen in the middle part and tapers towards base and apex is called fusiform root.
Example: Radish.
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| Fusiform root |
b) Conical:
The storage root which is borne at the base and gradually tapers towards apex is called conical root.Example: Carrot.
The storage root which is swollen, almost spherical and abruptly tapers into narrow apex. Is called Napiform root.
Example: Beet.
These are aerial roots found in mangrove plants i.e. plants growing in swamp or marshy places near the sea shores where the oxygen is lacking. To cope up with this situation the horizontal secondary roots give out aerial branches which grow vertically up-ward (negatively geotropic).
These aerial branches are called Pneumatophores which bear small pores called lenticels for gaseous exchange. Therefore, Pneumatophores are also called respiratory or breathing roots.
Examples: Rizophora, Avicennia etc.
B) Modification of Adventitious roots:
1) For Food storage:
a) Simple tuberous roots:
These roots become swollen and do not assume a definite shape. They are always borne singly. These roots arise from the nodes of stem and enter in the soil.
Example: Sweet potato.
B) Fasciculated tuberous roots:
A cluster of adventitious roots of some plants become thick and fleshy due to storage of food. These are known as fasciculated tuberous roots. There are many tuberous roots at the base of the stem.
a) Prop roots:
These roots from horizontal branches of trees like banyan tree and grow vertically downwards till they penetrate the soil. Secondary growth occurs in these roots, so that they become thick and act like pillars to provide mechanical support to the heavy branches.
Examples: Banyan.
Prop roots
b) Stilt roots:
These roots normally arise from a few lower nodes of a weak stem in some monocots, shrubs and small trees. They grow obliquely downwards and penetrate the soil and provide mechanical support to the plant.
Examples: Maize, Sugarcane, Jowar etc.
Examples: Maize, Sugarcane, Jowar etc.
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| Stilt root |
c) Clinging roots:
Climbing plants like piper produce roots from their nodes, by means of which they attach themselves to some support and climb over it.
Examples: Money plant, Piper (Betel).
Some small plants like orchids grow perched on horizontal branches of big trees in forest to get sunlight. Such plants have green leaves and can photosynthesize. These plants are called epiphytes.
Epiphytes are provided with these aerial roots in addition to the clinging roots. The aerial roots are spongy due the presence of special tissue called velamen, which is situated outside the cortex. The cells of velamen tissue are hygroscopic, have porous walls and with the help of this velamen tissue these roots absorb moisture from the atmosphere.
Examples: Vanda, Vanilla.
b) Sucking roots or Haustoria:
These are highly specialized and microscopic roots, developed by parasites to absorb nourishment from the host. In partial parasites like Loranthus they penetrate only xylem element of the host to absorb water and minerals.
In total parasites like Cuscuta they establish a connection with vascular strand of host and suck food directly from phoem and minerals from xylem, such root are called parasites roots, sucking roots or Haustoria.
This is the short information about the Modifications of roots that is Modifications of Tap root and Modifications of Adventitious roots etc.