Root modifications

 

Modifications of Tap Root In many plants the tap root becomes swollen and assumes various forms. This happens due to the storage of food. The modifications may be of the following:

 Fusiform- The root is swollen in the middle and gradually tapers towards both sides, e.g. radish (Raphanus sativus). 

Napiform- The root is spherical, ball-shaped, and wider than high and tapers down, e.g. turnip (Brassica rapa). 

Conical-  The root is cone like, tapering smoothly from base to tip, e.g. carrot (Daucus carota)

 Tuberous- The roots are thick and fleshy, no definite shape, e.g. Mirabilis. 

Kinds of Adventitious Roots Adventitious root may be modified to carry on the storage of food, mechanical support and other vital functions. Some of the main types are: Storage of food

 Tuberous- These roots arise from nodes of stem and become tuberous and fleshy, e.g. sweet potato (Ipomoea batatus). 

Fasciculated- Several fleshy tuberous roots produced grow in clusters at the base of the stem, e.g. Asparagus and Dahlia. 

Annulated- When the root has a series of ring like swelling without any gap, just like larvae of butterfly, e.g. Ipecac. 

Moniliform or beaded-  Such type of root swells at different places forming a beaded structure, e.g. bitter gourd (Momordica charantia) and Vitis.

 Nodulose- The slender root swells suddenly at its tip for storage of food, e.g. mango-ginger (Curcuma amada). 

Mechanical support Prop roots-  There are large pillar like roots, which appear from large horizontal branches. These roots grow downwards, which may finally enter into soil, e.g. banyan (Ficus bengalensis). 

Stilt roots- There are cluster of roots that grow obliquely downwards from near the base of the stem, e.g. screw-pine (Pandanus) and maize (Zea mays). 

Climbing roots- These roots arise from the nodes and internodes of many climbers. They help the plants in fixing themselves to their support, e.g. betel vine (Piper betle), Pothos.

 Buttress roots-  Such roots arise from basal parts of main stem and spread in different directions in the soil. They are irregular, thick, and broad like planks of wood, e.g. Bombax. 

Floating roots-  In Jussiaea, an aquatic plant, tufts of spongy, soft and light roots arise from the nodes in addition to ordinary adventitious roots. These roots have innumerable air spaces and thus help in maintaining buoyancy and facilitate respiration. 

Epiphytic roots-  Such roots are found in epiphytes. These roots hang in the air. These roots have a spongy tissue called velamen. It helps in the absorption of moisture from air, e.g. Vanda (orchid). 

Vital functions Assimilatory or photosynthetic roots-  Roots of some plants develop chlorophyll and perform the function of photosynthesis, e.g. Trapa, Tinospora.

 Reproductive roots. Roots of same plants develop adventitious buds, which after separation from parent plant forms new plant, e.g. sweet potato (Ipomoea batatus). 

Sucking roots- In some parasite plant, adventitious roots arise from the plant and enter the host plant developing contact with xylem and phloem of host stem. Such roots are called haustoria, e.g. dodder (Cuscuta).