The roots may have two types of functions, those are, normal root function and special root function.
Normal root function:
The normal root function includes the mechanical root functions and physiological root functions.
What is the normal mechanical root function?
The mechanical root function includes the attachment and fixation of the plants to the soil and they form a close network to root system which forms a close association with these soil particles.
What is the normal physiological root function?
The absorption of water and mineral nutrients by active and passive means are the most important physiological functions of the root. Conduction is another physiological function. The absorb water and nutrients are conducted through the xylem elements of the root to different parts of the plant body. The trans-location of the prepared food takes place through the phloem elements from the source of leaves to this sink or root. 
And the food storage is also a physiological root function. The food prepared which is excess is stored in the tap root which may be swollen as in conical of carrot. The excess of starch is stored as storage starch or fat. Due to the presence of this stored food the structure become very useful organs which surpass the unfavorable condition and germinate produce new plants.
Special root function: –
This special root function may also be divided into two types; those are mechanical function and physiological function. Now we have some discussion:
What is the special mechanical root function?
Prop Roots
The prop roots support like a pillar to the heavy branches specially which are more horizontal in nature such as banyan tree. The plants which have the week stem and bend towards the soil and hence supported by the stilt roots from one site of the leaning stem such as screw pine.
Floating Roots
The climbing roots develop from the notes of creepers and help it climbed around a solid support to words the light, such as betel. Some roots contract from one point and develop in some other area keep the stem idiot and those are called contractile roots, such as onion. There have other types of root which are called floating root. These roots contain parenchyma and provide buoyancy to floating hydrophytes, such as the Jussiaea.
What is the special physiological root function?
One of the special physiological root functions is the storage root. This type of root such as sugar beet, radish and sweet potato are helping in storage of food. The assimilatory roots contain chlorophyll and it helped to prepare food by photosynthesis. Tinospora is the example of such root. There is also having the breathing roots. These roots exhibit positive phototropic movement to absorb air for respiration as these soil in which they grow, are inadequately aerated.