Root Modifications
வேர் உருமாற்றங்கள்
Pneumatophores grow upward, against gravity, out of the mud — because mangrove roots are starved of oxygen. If you remember 'Rhizophora breathes through its knees', you will never miss this one.
The idea
Roots are modified for storage, support and respiration. Tap roots of carrot and turnip and adventitious roots of sweet potato swell to store food. Prop roots hang down from the branches of the banyan tree and support it. In maize and sugarcane, stilt roots arise from the lower nodes of the stem. In plants growing in swampy areas, such as Rhizophora, many roots come out of the ground and grow vertically upwards; these pneumatophores get oxygen for respiration. In free-floating water plants like Pistia, the roots play little role in water absorption because water is absorbed over the whole surface.
Why it matters
Roots must anchor, absorb, store and breathe; when soil is waterlogged or a tree is huge, ordinary roots are not enough, so they change shape.
NEET lens
NEET pairs: pneumatophores = Rhizophora (mangrove halophytes, swampy saline soil); prop roots = banyan; stilt roots = maize, sugarcane; storage tap root = carrot, turnip; storage adventitious root = sweet potato. 'Roots play insignificant role in water absorption in' — Pistia (free-floating hydrophyte).
Clinical significance
Mangrove forests with pneumatophores (like the Pichavaram mangroves in Tamil Nadu) protect coasts from cyclones and tsunamis. Storage roots such as carrot, radish and sweet potato are important foods.
Introduction
Besides anchorage and absorption, roots of some plants are modified to store food, give extra support or help in respiration.
Core concept
Storage: tap roots of carrot, turnip; adventitious roots of sweet potato. Support: prop roots of banyan (hang from branches); stilt roots of maize and sugarcane (from lower nodes). Respiration: pneumatophores of Rhizophora — roots grow vertically upwards out of the swampy ground to get oxygen.
Go deeper
Pneumatophores occur in halophytes of mangrove swamps, where waterlogged saline mud has almost no oxygen. In floating hydrophytes like Pistia, roots are reduced in function because the whole plant is in water.
From Class 10
Roots usually grow down into the soil. Some roots grow from branches or even upwards — when the plant needs extra support or air.