Explain various types of adventitious roots which are modified for mechanical support.

1. Prop roots / Columnar roots: 

a. These roots arise from horizontal branches of tree like Banyan tree (Ficus benghalensis) and grow vertically downwards till they penetrate the soil. 

b. These prop roots show secondary growth, become thick, act like pillars to provide mechanical support to the heavy branches. 

2. Stilt roots: 

a. These roots normally arise from a few lower nodes of a weak stem in some monocots, shrubs and small trees. 

b. They show obliquely downward growth penetrating soil and provide mechanical support to the plant. 

c. In the members of family Poaceae, the plants like Maize, Jowar, Sugarcane etc. produce stilt root in whorl around the node. 

d. These roots provide additional support to the plant body. 

e. In Screw pine or Pandanus (Kewada), stilt roots arise only from the lower surface of obliquely growing stem for additional support. These roots show multiple root caps.  

3. Climbing roots: 

Different climbers with weak stem produce roots at their nodes by means of which they attach themselves to support and thereby raise themselves above the ground. e.g. Betel leaf or Pan, black pepper or Piper nigrum (Kali Mirch), Pothos or money plant. 

4. Clinging roots: 

a. These tiny roots develop along intemodes, show disc at tips, which exude sticky substance. 

b. This substance enables plant to get attached with walls of buildings. 

c. They do not damage substratum, e.g. English Ivy (Hedera helix).

5. Plank roots/Buttress: 

a. These roots often develop at the base of large trees and form plank like extensions around stem. 

b. These roots provide additional support, e.g. Silk cotton, Peepal, etc. 

6. Buoyant roots: 

Roots developed at the nodes of aquatic herbs like (Jussiaea repens), become highly inflated and spongy providing buoyancy and helping the plant to float.