STRUCTURAL ORGANISATION IN PLANTS AND ANIMALS

5.1 THE ROOT

The root is the underground part of a flowering plant that primarily anchors the plant to the soil and absorbs water and minerals necessary for growth. In dicotyledonous plants, the root system is typically a tap root system, which originates from the radicle of the embryo. The radicle elongates directly to form the primary root, which grows deep into the soil and produces lateral roots of various orders such as secondary and tertiary roots. These collectively form the tap root system, exemplified by plants like mustard. In contrast, monocotyledonous plants generally have a fibrous root system, where the primary root is short-lived and replaced by numerous roots arising from the base of the stem, as seen in wheat. Additionally, some plants develop adventitious roots that arise from parts other than the radicle, such as stems or leaves; examples include grass, Monstera, and banyan tree. The root system performs several vital functions: it absorbs water and minerals from the soil, provides mechanical support and anchorage to the plant, stores reserve food materials, and synthesizes plant growth regulators that influence development and growth.

• Dicot plants have a tap root system originating from the radicle.
• Monocot plants have a fibrous root system with roots arising from the stem base.
• Adventitious roots arise from parts other than the radicle.
• Roots absorb water and minerals, anchor the plant, store food, and synthesize growth regulators.
• Tap root system includes primary root and its lateral branches.
• Fibrous root system consists of numerous roots of similar size.
• 📌 Tap root system: Root system with a main primary root and lateral branches.
• 📌 Fibrous root system: Root system with many roots of similar size arising from the stem base.
• 📌 Adventitious roots: Roots arising from parts other than the radicle.

5.1.1 Regions of the Root

The root tip is structurally divided into distinct regions that perform specific functions essential for root growth and development. At the very apex of the root is the root cap, a thimble-like protective structure that shields the delicate meristematic cells as the root pushes through the soil. Just above the root cap lies the region of meristematic activity, where cells are small, thin-walled, and densely packed with protoplasm. These cells divide actively, contributing to root growth. Above this is the region of elongation, where cells increase rapidly in length and volume, pushing the root tip further into the soil. Following the elongation zone is the region of maturation, where cells differentiate into various specialized types. In this zone, some epidermal cells develop into root hairs, which are fine, thread-like extensions that greatly increase the surface area for absorption of water and minerals from the soil. These regions work in coordination to ensure continuous root growth and efficient absorption.

• Root cap protects the root apex during soil penetration.
• Region of meristematic activity contains actively dividing cells.
• Region of elongation involves rapid cell enlargement for root lengthening.
• Region of maturation is where cells differentiate and root hairs develop.
• Root hairs increase surface area for absorption.
• Each region is essential for root growth and function.
• 📌 Root cap: Protective structure at root tip.
• 📌 Region of meristematic activity: Zone of active cell division.
• 📌 Region of elongation: Zone where cells elongate to increase root length.