Root developing from any part of the plant other than radicle is called adventitious root.
It may develop from the base of the stem or nodes or internodes. Example: Monstera deliciosa, Ficus benghalensis, Piper nigrum. In most of the monocots the primary root of the seedling is short lived and lateral roots arise from various regions of the plant body. These are bunch of thread-like roots equal in size which are collectively called fibrous root system generally found in grasses. Example: Oryza sativa, Eleusine coracana, Pennisetum americanum.
Adventitious root modification
These roots are swollen without any definite shape. Tuberous roots are produced singly and not in clusters. Example: Ipomoea batatas.
These roots are in cluster from the base of the stem Example: Dahlia, Asparagus, Ruellia.
In this type of roots swelling occurs only near the tips. Example: Maranta (arrow root) Curcuma amada (mango ginger), Curcuma longa (turmeric)
These roots swell at frequent intervals giving them a beaded appearance. Example: Vitis, Portulaca, Momordica, Basella (Indian spinach).
These roots have a series of ring- like swelling on their surface at regular intervals. Example: Psychotria (Ipecac)
These roots grow vertically downward from the lateral branches into the soil.
Example: Ficus benghalensis (banyan tree), Indian rubber.
These are thick roots growing obliquely from the basal nodes of the main stem. These provide mechanical support.
Example: Saccharum officinarum, Zeamays, Pandanus, Rhizophora.
These roots are produced from the nodes of the stem which attach themselves to the support and help in climbing. To ensure a foothold on the support they secrete a sticky juice which dries up in air, attaching the roots to the support. Example: Epipremnum pinnatum, Piper betel, Ficus pumila.
In certain trees broad plank like outgrowths develop towards the base all around the trunk. They grow obliquely downwards and give support to huge trunks of trees. This is an adaptation for tall rain forest trees. Example: Bombax ceiba (Red silk cotton tree), Ceiba pentandra (white silk cotton tree), Terminalia arjuna, Delonix regia, Pterygota alata.
c. Vital functions
Some epiphytic orchids develop a special kind of aerial roots which hang freely in the air. These roots develop a spongy tissue called velamen which helps in absorption of moisture from the surrounding air. Example: Vanda, Dendrobium, Aerides.
Roots are produced from the veins or lamina of the leaf for the formation of new plant. Example: Bryophyllum, Begonia, Zamioculcas.
These roots are found in parasitic plants. Parasites develop adventitious roots from stem which penetrate into the tissue of the host plant and suck nutrients.
Example: Cuscuta (dodder), Cassytha, Orobanche (broomrape), Viscum (mistletoe), Dendrophthoe.
Roots of some climbing or epiphytic plants develop chlorophyll and turn green which help in photosynthesis. Example: Tinospora, Trapa natans (water chestnut), Taeniophyllum.