Root - Its type and modifications

 

The plant embryo inside the seed contains some structures like plumule radicle and leaf primordia. Out of these structures, the radicle is responsible for the formation of roots. Roots are so important for the plant because in addition to   providing the anchorage, they  absorb  and transport the minerals and water  from the soil through the root hairs.

Roots and its accessory roots collectively form a root system in plant kingdoms. There are different  types of root systems. Tap root, fibrous root  and Adventitious root system.

After the germination of seed, the first root-like structure that is  originated from the radicle is called primary root. There are several  lateral roots that originate from the primary root, called as secondary roots, tertiary root and so on. These primary, secondary and tertiary roots collectively constitute the tap root system. For Example- Radish carrot The tap root system  increases the surface area for water and mineral absorption. 

In other plants, the taproot is modified into a fibrous root system. A large number of roots originate from the base of the stem so there are no remains of well-defined single taproot.Such root system is fibrous.root system. For Example- wheat coconut

When  roots arise from the other parts of plants like stem and leaves called adventitous root systems. 

Modifications of Roots

When root performs other functions than its own function like absorption of mineral and water  and anchorage, called root modifications. All root systems taproot adventurous root are involved in its modification as per the need that is stimulated by the environmental conditions.

Types of Tap root on the basis of modification 

In some plants, tap roots are meant for the storage of reserve food. As a result, the primary root or main root of the tap root system of these plants become fleshy and swollen. The swollen roots may exist  in different shapes. On the basis of the shape due to storage of food,  The types of tap roots are as follow

When the  main root assumes the  conical shape with a broad base but it tapers when it grows at the apex. It is called conical tap root. CARROT. The  main root assumes a  spherical shape and  tapers at the tip called Napiform. TURNIP In Fusiform type, The main root is swollen in the middle and tapers at both the ends. RADISH. In the tuberous type of root, the main root has no permanent shape. 4OCLOK PLANT  

In Legume plants like PEA GRAM  there is swelling  on their main root as well as on their branches called root nodule and it is called root nodule formation. These nodules have nitrogen fixing bacteria called Rhizobium which fix atmospheric nitrogen into nitrates and supply them to the plants.                            

Types of adventitous root on the basis of modification

Like the tap root, adventitious roots also store reserve food and get swollen.On the basis of this, these roots are of  following types

In some plants, adventurous roots are  arisen from the nodes of the  stem and swollen due to storage of food but these have no marked shape. Such roots are called Tuberous roots. SWEET POTATO 

When the swollen roots are found in the form of  clusters at the base of the stem called Fasciculated root.DAHLIA 

In Nodulose root the tips of the roots become swollen due to accumulation of food.GINGER.

When the roots are swollen at random places and provide a beaded appearance called  Moniliform root BITTER GOURDS

In some plants like the ORCHID the stem and leaves are absent and only aerial roots are present which contain a  tissue called velamen. These roots remain   free in air and absorb moisture from air with the help of velamen. Such roots are called epiphytic or hygroscopic Roots

The plants that are present in  mangrove or marshy soil, develop some aerial roots. They grow vertically up into the air. Such roots are called breathing roots or pneumatophores. These roots have numerous pores called lenticels at the tips through which respiratory gasses are diffused inside and outside the plant body. RHIZOPHORA.