Modifications of roots (storage, support, respiration)

1. Introduction

1. Roots are the underground part of the plant that provides anchorage and absorption.
2. In some plants, roots are modified to perform specialized functions.
3. Root modifications are classified into three major types: Storage, Support, and Respiratory roots.

2. Storage Roots

1. Storage roots store excess food in the form of starch, sugars, and other nutrients.
2. These roots become thick and swollen to serve as food reservoirs.
3. Common in biennial and perennial plants.

Types of Storage Roots

1. Conical Roots: Broad at the base and tapering towards the apex (e.g., carrot).
2. Fusiform Roots: Swollen in the middle and tapering at both ends (e.g., radish).
3. Nodulose Roots: Swollen at the tips (e.g., mango ginger).
4. Tuberous Roots: Irregularly swollen roots without a definite shape (e.g., sweet potato).
5. Napiform Roots: Spherical or top-heavy roots tapering suddenly (e.g., turnip, beetroot).

3. Support Roots

1. Support roots provide additional anchorage and stability to plants.
2. They are mainly found in large trees and weak-stemmed plants.

Types of Support Roots

1. Prop Roots: Grow from branches and descend vertically to the ground for support (e.g., banyan tree).
2. Stilt Roots: Arise from lower nodes of the stem and provide extra support (e.g., maize, sugarcane, screwpine).
3. Climbing Roots: Help climbers attach to a surface (e.g., betel, black pepper).
4. Buttress Roots: Horizontally spreading roots that support tall trees in tropical forests (e.g., silk cotton tree).

4. Respiratory Roots

1. Respiratory roots, also known as pneumatophores, help in gaseous exchange in plants growing in waterlogged or swampy regions.
2. These roots grow vertically above the ground and possess tiny pores (lenticels) for oxygen intake.
3. Common in plants growing in mangrove ecosystems (e.g., Rhizophora, Avicennia, Sonneratia).

5. Other Specialized Root Modifications

1. Parasitic Roots: Found in parasitic plants that penetrate the host to absorb nutrients (e.g., Cuscuta, Orobanche).
2. Epiphytic Roots: Found in plants growing on other trees, helping in moisture absorption (e.g., orchids).
3. Contractile Roots: Help in pulling underground structures deeper into the soil (e.g., onion, crocus).

6. Conclusion

1. Roots not only provide anchorage and absorption but also perform various specialized functions.
2. Modifications like storage, support, and respiration help plants adapt to different environmental conditions.
3. Understanding root modifications is essential for plant classification and agricultural applications.