Root Modifications – Tap Root & Adventitious Roots

Modification of Roots is the process by which roots alter their shape to absorb and transport water and minerals from the soil to various parts of the plant. In addition, the function of roots includes absorbing water and minerals and transporting them to the stem, storing food, and providing support to the plant body. Root modifications emphasize a plant’s ability to survive. This article explains the modifications of roots, focusing on the modification of taproot and adventitious root systems.

Root Modification Definition

Modifications of Roots can be defined as the structural and functional changes that roots undergo to adapt to specific roles such as absorption, storage, support, or aerial functions in plants.

What are the Modification of Roots?

Root modifications reflect the process of evolution, where plants continuously adapt to changing conditions to enhance their growth and survival. The word “modifications of roots” describes the anatomical and functional alterations made to a plant’s roots in order to perform a variety of tasks and adapt to certain environmental circumstances. In addition to taking in water and nutrients and occasionally storing food, roots are vital plant parts that help plants remain grounded in soil.

Diagram of Root Modification

The different types of modified roots diagram are shown below:

Types of Root Systems

Based on their shape and role, root systems are of two types- tap root system and adventitious root system.

Tap Root System

The Tap Root System has a central root that grows vertically downward and gives rise to lateral (branch) roots. These roots’ primary function is to provide strong anchorage and efficient absorption of water and nutrients from deeper soil layers. Plants that possess tap root systems include carrots, radishes, dandelions, oak trees, etc.

Adventitious Root System

The roots of the adventitious root system originate from plant parts other than the primary root, such as stems, leaves, or even other roots. This system helps in various functions such as support, propagation, and nutrient absorption from the surface soil layers. Plants that possess adventitious root systems include grasses, wheat, rice, etc.

Modification of Tap Roots

There are various reasons for tap root modification including food storage, nitrogen fixation, and respiration process. Let’s discuss these reasons in detail.

Tap Root Modification for Food Storage

In various plants, the central root of taproots needs to store food and due to this they become fleshy and swell up. The branched roots, however, are, involved in the absorption of minerals from the soil. Depending on the type of root, the central root swells up and assumes different shapes. On the basis of these shapes, tap roots may be classified as:

• Conical roots: This type of taproot assumes the shape of a cone and grows vertically downward. For example, Carrots
• Fusiform Roots: This type of taproot becomes swollen or turnip shaped. For example, Radish
• Napiform Roots: This taproot type is spherical at its base and tapers at both ends. For example, Turnip
• Tuberous Roots: This type does not assume any shape and develops swellings along its length. For example, Sweet Potato.

For Nitrogen Fixation

Various crops of the leguminaece family including plants like peas, groundnuts, and grams possess root nodules. Millions of nitrogen fixing bacteria known as Rhizobium, inhabit these nodules and convert atmospheric nitrogen into nitrates which is later used by the plant’s roots.

For Respiration Process

Several plant varieties grow in saline marshes, these plants are known as mangrove plants. The roots of these plants are deprived of oxygen. To remedy this situation some branches of the secondary roots grow vertically up i.e. a few branches from the secondary roots emerge out from the marsh and grow upwards for better respiration.

Modification of Adventitious Roots

Modifications of Adventitious Roots occur due to various reasons related to the plant’s adaptation to its environment and specific functions including support, food storage, moisture absorption, reproduction, floating, fungal symbiosis, and photosynthesis.

Supportive Roots

When plants are tall or heavy, adventitious roots modify to provide additional support. Various types of adventitious roots offer support to a plant including:

• Prop Roots: These roots grow downwards after emerging from the existing branches of the tree, and anchor into the ground upon reaching the soil.For example, banyan tree.
• Stilt Roots: Various small trees and shrubs grow in places where the anchorage is not strong like on the edges of tanks. In these cases, small roots grow diagonally downwards from the base of the stem, providing additional support like stilts. For example, Sugarcane plant
• Climbing Roots: Arising from the nodes, these roots attach themselves to a support and climb up using it, therefore providing support to the plant. For example, Money plant
• Clinging Roots: To hold the plant, these roots enter the gaps present on the support and anchor the plant. For example, orchids
• Buttress Roots: These develop at the base of a stem and are spread in different directions in the soil. These roots look like planks and prevent the tree from falling. For example, Bombax.
• Floating Roots: These roots found in certain aquatic plants like water hyacinth, water lettuce, etc., help the plant float. Additionally, it also helps the plant in nutrient absorption and respiration.
• Contractile Roots: These roots possess the ability to contract or shorten their length. This ability helps the plant to pull itself deeper into the soil, providing increased anchorage, and stability.
• Root Thorns: These roots, due to various environmental factors, evolve into sharp, pointed structures that serve various functions including protection and anchorage.

Food Storage

Some adventitious roots undergo modifications to store nutrients efficiently. These include:

• Tuberous: These roots assume no shape but swell up upon storing food. Additionally, these roots arise from the nodes of the prostate stem. For example, sweet potato.
• Fasciculate: These roots, upon swelling up, assume a definite shape and grow in clusters at the stem base. For example, dahlia and asparagus.
• Nodules: In these roots, the apex of the roots swell up upon the storage of food, For example. mango, and ginger.
• Moniliform: The roots are beaded at fixed intervals upon the accumulation of food—For example, bitter gourd.
• Annulated: These roots give the appearance of numerous discs placed one on top of the other. For example, Ipecac.

Moisture Absorption

Adventitious roots known as epiphytic roots are aerial roots that hang from the plant’s body and have a porous wall that absorbs moisture from the atmosphere. As these plants have no contact with the soil, Velamen, a tissue present on these roots, absorbs and stores moisture. For example- Orchids.

Reproduction

In many plant species, adventitious buds grow on roots and plantings arise from the base. For example, sweet potato, and ipecac. Additionally, various plants with adventitious roots can reproduce vegetatively i.e. they can form from stems, leaves, or other non-root tissues, without the requirement for seeds.

Floating

The nodes of aquatic plants give rise to these roots which aid in both flotation and respiration. The plant remains buoyant in water due to the spongy nature of these roots, but when removed from their aquatic environment, these roots dry up. For example, Jussiaea.

Fungal Symbiosis

A type of adventitious root also known as mycorrhizal root is home to fungal hyphae. The fungus present absorbs water and minerals from the soil for the plant, and the plant, in return, provides the fungus with organic food. For example, Pinus

Photosynthesis

Adventitious roots known as assimilatory roots are specialized roots that help in the uptake, conversion, and storage of nutrients and minerals in plants. Upon exposure to the sun, these roots develop chlorophyll and assimilate some carbon. Using these two components, these roots prepare food for the plants. These roots also play an important role in enhancing plant metabolism, and growth. For example, Tinospora

Haustoria Roots

These are specialized adventitious roots that penetrate the host plant tissue and absorb the water and nutrients. Haustoria roots help a parasitic plant survive and grow by facilitating its nutrient uptake from the host plant.

Modification of Fibrous Roots

Fibrous roots are characterized by numerous thin roots that arise from the base of the stem. These roots are similar in girth and form a dense, interconnected network. These roots are typically found in monocots, such as grasses, lilies, and orchids.

Storage

Various plants, such as sweet potatoes, possess fibrous roots that undergo modification, transforming into storage roots. These specialized roots store carbohydrates, providing a valuable source of food and nutrition.

Pneumatophores

Root modifications in mangrove trees occur as fibrous roots may develop pneumatophores which are specialized structures that extend above the water surface to facilitate oxygen uptake in waterlogged soils.

Nitrogen Fixation

Despite having fibrous roots, some plants such as the white clover have the ability to form nodules. These nodules host nitrogen-fixing bacteria, which convert atmospheric nitrogen into a form fit for the plant therefore enhancing soil fertility.

Reproduction

In various plant species with a fibrous root system, buds develop on the roots. These buds play a role in vegetative propagation, wherein, under favorable conditions, they can develop into a separate new plant.

Importance of Modifications of Plant Roots

Modifications of Roots is an essential adaptation technique that helps in processes like nutrient absorption, water uptake, anchorage, protection, and reproduction.

1. Nutrient Absorption: Various plant species form symbiotic relationships with mycorrhizal fungi, which help in nutrient absorption from the soil, particularly enhancing the uptake of phosphorus and nitrogen.
2. Water Uptake: The plants that grow in waterlogged soils or marshy environments develop aerenchyma (soft plant tissue that consists of air spaces), which helps in the exchange of gases and improves oxygen uptake for roots.
3. Anchorage: Modifications like prop and buttress roots provide anchorage to the plant i.e. it provides the plant with additional support, specifically in regions with poor soil or extreme weather conditions.
4. Reproduction: In various fibrous-rooted plants, roots develop buds that give rise to new plants, helping in reproduction and spreading.

Conclusion – Modifications of Roots

Root modification is a fascinating example of how plants adapt and survive in various environments. Modified roots alter in both shape and function to facilitate plants to mature well in different places. For example, various roots support plants, while others help them absorb moisture from the air or allow them buoyancy. By studying these modification of roots, we gain insights and learn more about plants’ evolutionary cycle and adaptable nature.

FAQs – Modifications of Roots

What are the Modifications of Tap Roots?

Tap roots can be shaped into a variety of forms to carry out particular tasks, such food storage. Fusiform, Napiform, Conical, Tuberous, and Tubercular are examples of modified tap roots.

What are the 4 Types of Roots?

The four types of roots are: Tap Roots , Fibrous Roots, Adventitious Roots and Aerial Roots

What are the Modifications of Monocot and Dicot Roots?

Modification of monocot root feature a fibrous root system with distributed vascular bundles and no main root. Modification of dicot root feature a taproot system that consists of a noticeable main root and lateral branches.

How do Modified Roots provide Support Plants?

Modified roots, such as taproots and adventitious roots, anchor the plant firmly into the soil, ensuring stability against winds, rains, and other environmental factors.

Which Root System, the Taproot or Adventitious root, typically stores a Greater amount of Food for the Plant?

While both taproots and certain adventitious roots store food, taproots are generally more specialized and store larger quantities of nutrients for the plant’s use.

What are the 5 Root Modifications?

Modified root systems are Storage root, Aerial roots, Parasitic roots, Buttress roots, Prop roots and Reproductive roots.