Define root. Mention the types of root systems. Explain how root is modified to perform different functions?

Root : It is an underground part of the plant axis developed from the radical of the germinating seed. Root systems are two types.
a) Tap root system : In dicots the radical of the seed developed into the primary root and it branches constitute the tap root system.
b) Fibrous root system : In monocots the radical of the seed is short lived and at the base of the stem produce a cluster of unbranched roots to form fibrous root system.
Root modifications :
1. Storage roots : In some plants roots become swollen and tuberous due to storage of food. Storage root may be a tap root.
Eg: Carrot, Radish, Turnip
Storage root may be adventitious root and form fasciculated tuberous roots.
Eg: Asparagus.
2. Prop roots : The aerial adventitious roots arises from the branches and reaches the soil appear as pillar like to give mechanical support to plant.
Eg: Banyan tree
3. Stilt roots : These roots develop from the lower nodes of the stem and gives additional support to plant. Eg: Maize, Sugarcane.
4. Assimilatory roots : In some plants chlorenchymatous roots synthesise starch by Photosynthesis.
Eg: Taeniophyllum (Epiphyte)
5. Nodular roots : In Fabaceae members, roots having nodules called as nodular roots. Nodular roots posses symbiotic bacteria Rhizobium helps in nitrogen fixation.
Eg : Groundnut and Beans.