Modification of Root
1. Roots for storage
Look at a radish, turnip, beet root, and carrot. They all grow under the soil. As soon as you pluck it from the ground if you wash them gently, you will notice small roots dangling from their surface. All these vegetables are in fact roots of the plant. Instead of thin slender roots, in case of such plants, the roots have become a place to store the food produced by them.
Hence they are thick and swollen. One can notice that the tap root of radish is in the shape of spindle, swollen in the middle and tapering at both ends. Such type of modified roots are called spindle shaped root. Example : Radish
At times, like in the case of turnip, and beet root the tap root can acquire a shape of top, that is spherical at the base and tapering shortly towards the apex. They are called as Top shaped root.
In case of carrot, the shape is conical, broad at the apex and tapering gradually towards the base and such modified roots are called Conical shaped root.
Aim: To study the modification of root.
Materials Required: Sample / charts of raddish, carrot, beet root, sweet potato, stilt roots and pneumatophores.
Procedure: Carefully observe the shape of each specimen.
Observation: Draw the diagram and observe the morphological differences between the samples.
2. Mechanical Support
Look at a banyan tree. It seems to have many trunk supporting it. However many of them are actually roots. As the banyan tree is large and huge, it needs support not to tilt and fall down. Many plants require such additional support. Such plants develop roots on their aerial parts to provide mechanical support. These roots grow downward and act as supportive organs. There are three types of modified roots for support.
i. Prop roots: Roots are modified to provide mechanical support as seen in Banyan tree. These roots grow vertically from horizontal branches of a tree.
ii. Stilt roots : In sugar cane, and maize adventitious roots arise from the nodes in cluster at the base of the stem. These roots are called stilt roots which gives additional support.
iii. Climbing roots: In betel and black pepper, nodes or intermodes bear roots which help in climbing.
A root growing from a location other than the underground, such as from a stem or leaf is called as adventitious root
3. Gaseous Exchange:
Avicennia is a tree which grows in mangroves or swamps. They have roots which are seen above the ground for the purpose of gaseous exchange. These roots are erect, peg like structures with numerous pores through which air circulates. These roots are called breathingroots, or pneumatophores.
Vanda is an epiphytic plant, which grows on trees. Thevelamen tissue present in the epiphytic root, absorbs moisture,to perform photosynthesis
4. Roots for other vital function
Roots may also be perform special function. Haustoria or Sucking roots, are one such example. Cuscuta a parasite plant, climb the trees and other vegetation and use the haustorial roots to penetrate the tissue of the host plant and suck nutrients from them. They are usually found in parasitic plants that depend on the host plants for nutrients.