2. ROOT MODIFICATION TO PROVIDE ADDITIONAL MECHANICAL SUPPORT:
(a)Prop roots: These adventitious roots arises from the aerial branches of tree they grow downward having root cap hygroscopic ( absorb water from air ) then enter the soil act like a pillar provide support to the growing tree like stem and in very old trees it is difficult to differentiate between main stem and pillar or prop roots.Ex. Ficus bengalensis.
(b) Stilt roots: Plants having delicate stem develop short and thick oblique supporting roots from basal portions of stem they penetrate into the soil provide support to the plant and help in absorption of mineral and water. Ex. Sugarcane, Maize
(c)Climbing roots : These roots arises from the nodes and twin around the support .These are present in climbers.Ex. Ivy
3. ROOTS TO PERFORM VITAL FUNCTIONS:
(a)Assimilatory roots or Photosynthetic roots:In some plants the roots develop chlorophyll and perform the function of photosynthesis i.e they prepare the food with the help of CO₂ & water in presence of light .Ex. Tinospora, Trapa
(b) Haustorial roots: Roots which are present in parasitic plants they penetrate into the host tissue and absorb water mineral & food.Ex Cuscuta.
(c)Floating roots: Develop from nodes store air and are spongy so float above the water .Ex. Jussiaea
(d) Epiphytic roots : These roots develop in some orchids which grow as epiphytes upon the trunks of branches of trees .They hang freely in the air and absorb moisture with the help of special sponge like tissue called velamen. Ex. Vanda
(e) Contractile or pull roots: In Plants with underground stem the roots contract or swell so that the aerial shoot kept in the proper depth in soil are pull roots. Ex. Crocus , Allium.
(f) Reproductive roots: Roots develop buds and help in vegetative reproduction .Ex Sweet potato.
(g)Leaf roots: In this leaf modified into roots .Ex. Salvinia In this out of three leaves one modified into roots .
(h) Root thrones: Roots from base of stem become hard & thorny but differ from stem thorn as endogenous in origin. Ex. Pothos armatus.
