Root Modifications

Introduction

Roots are the vital organs of plants that help in support and water and nutrition absorption and transport. There are 2 types of root systems:

• Tap root system

• Adventitious or fibrous root system.

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Tap Root

When a seed germinates, the radicle elongates and becomes a taproot or primary root. In dicotyledonous plants, the main root is persistent and produces lateral roots.

All younger roots arise at the apex and older roots at the base. The taproot and its branches form the taproot system.

Adventitious Root

Adventitious roots grow from a part of the plant other than the radicle. In monocot plants, these are short-lived and later replaced by adventitious roots. All these form the adventitious root system.

In some plants, the roots modify themselves to absorb and transport nutrition from the soil to completely different elements of the plant. These are generally modified for support, food storage, and respiration.

It performs physiological and mechanical functions.

Modification of Tap Roots

There are various functions for which tap root modifies themselves such as food storage, respiration, etc.

Food storage

Some plant roots modify themselves for the absorption of nutrition. The aerial parts or parts which are above-ground of these plants wear down due to unfavorable conditions. When conditions are favorable again, new shoots will emerge, either from the fleshy root or from a small stalk above.

These type of roots are classified based on their shape.

Type	Example
Conical roots	Carrot
Tuberous roots	Sweet potato
Fusiform roots	Radish
Napiform roots	Turnip

Nodulated Roots for Nitrogen Fixation

The roots of legumes modify themselves to perform nitrogen fixation. It allows symbiotic association with nitrogen-fixing bacteria such as Rhizobium. These bacteria convert atmospheric nitrogen into nitrates.

Respiration

Halophytes like Rhizophora grow in swampy areas. Roots of such plants erupt from the ground and grow upwards to obtain oxygen for respiration. They have lenticels at root tip for breathing.

Modifications of Adventitious Roots

Adventitious roots are the roots that grow from a part of the plant other than the radicle. It shows the following types of modifications.

Food Storage

• Simple Tuberous Roots: These are the modified adventitious roots. They are fleshy, swollen and have no particular shape. For example, Sweet Potato.

• Fasciculated roots: The fasciculated roots appear in the form of clusters that arise from their stem base. For example, Dahlia.

• Moniliform roots: These roots are also swollen. However, moniliform roots periodically swell, and give the roots a bead-like appearance. For example, Rose moss.

• Annulated roots: These are a series of outgrowths on the body that shows the ring shape. The rows of these growths look like discs stacked on top of each other. For example, Ipecac.

• Nodulose Roots: Nodulose roots are modified adventitious roots that swell at the apex or tips and have a characteristic shape. For example, Turmeric.

Mechanical strength

• Prop Roots: Plants like bamboo and banyan have heavy branches with hanging roots. They give the tree trunk additional support. They penetrate the ground and support branches of the tree. These roots are long and pillar shaped. Hence, also known as columnar roots. They possess lenticels for respiration.

• Stilt Roots: Some plants show growth of additional buttress roots at the lower nodes of the main stem. These roots grow obliquely downwards and penetrate the soil. It supports the plant to stand upright and is known as stilt roots. For example, Sugar Cane, Corn.

• Climbing Roots: Some plant roots arise from the nodes and internodes. With the help of these roots, the weak stems of the climber’s twine around the support. These are also known as tendrillar roots. For example, Betel, Black pepper and Ivy.

• Clinging Roots: This type of modified root is short, branching adventitious roots. Generally, found on epiphytes. For example, Orchids, Piper betel.

Additional Functions

• Photosynthesis: Assimilatory roots when exposed to the sun form chlorophyll and create their own food by photosynthesis. For example, Tinospora (orchid).

• Reproduction: The roots of some plants help in vegetative reproduction and produce new shoots. For example, sweet potatoes.

Conclusion

Roots are vital parts of a plant. They mainly offer support and absorption and transport of nutrients from the soil. Tap root systems and adventitious root systems are major types of root systems seen in plants. In some plants, we can see beyond anchorage and water and mineral transport, roots can perform some advanced functions which show modifications in their root system.

Generally, roots are modified to store food, provide mechanical support, reproduction, photosynthesis, etc. Based on their modified functions and shape they can be categorized into various classes.

FAQs

Q1. Do aquatic plants have roots?

Ans: Yes. The roots of aquatic plant life are quick in order that water can effortlessly unfold via the leaves. The aquatic plant life has fibrous roots as they do now no longer require an inflexible shape as water strain offers guidance to the plant. The fibrous roots assist the aquatic plant life to float. Hence, the roots of aquatic plant life are quick and fibrous.

Q2. What is ectomycorrhizae?

Ans: In mycorrhizal roots, fungi and plants get mutually benefited. Some plants are ectomycorrhizae wherein the hyphae develop at the floor of the roots. For example, Monotropa and Sarcodes.

Q3. How do pneumatophores help in respiration?

Ans: Some plants grow in marshy soils, increasing a few aerial roots. They grow aerially, such roots are known as respiratory roots or pneumatophores. They have conical spikes like structure and several pores known as lenticels on the hints via which gases diffuse in and out. For example, Rhizophora.

Q4. What are contractile roots?

Ans: Some plants show modified adventitious roots at the base of underground stems known as contractile roots. It contracts and swells to keep the aerial shoots at the right depth in the ground. For example, Canna and Allium.

Q5. Why are some plants known as parasitic plants?

Ans: Some plants possess sucking roots which are a type of modified roots. These are advanced through the roots to soak up vitamins from the host. These also are called parasitic roots or haustorium roots. These roots penetrate into the host tissue and get their nutrition.