Download Modification of Stem PDF:General Science Notes

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Download the Modification of Stem General Science notes in PDF. Learn about the different types of stem modifications, such as thorns, stolons, and tubers, and their roles in plant growth, reproduction, and defence.

Question – Potato is a modified _____:
A. Stem
B. Root
C. Leaf
D. None of these

My dear friends, you will encounter the above question in almost all competitive exams, especially in the SSC and Railway exams. The question belongs to the topic “Modification of Stem”. It is a part of the chapter “Morphology of Flowering Plants” in Biology. Here is a detailed note on ‘Modification of Stem’ with examples.


• The stem is the main structural axes of a vascular plant that bears shoots, leaves, buds, nodes, internodes, and the basal end-roots.

• It conducts water, minerals, and food to other parts of the plant body through various systems.

• In some plants, the stem is modified to perform different functions such as…
• Storage of food
• Support of plants
• Vegetative propagation
• Protection from animals

• These are modified stems and can be categorized into various classes.

Modification of Stem with Examples

• Based on the purpose and functions, stem modification can be classified into the following categories.

1. Underground modifications
2. Subaerial modifications
3. Aerial modifications

• Let’s discuss all three categories one by one ______

Underground modifications of Stem

• The Underground Stems of this type of plant are modified for perennation and storage of foods.
• These plants produce aerial shoots annually.

Perenniality is the ability of a plant to survive from one germination season to another under adverse conditions such as drought or winter.

• These underground stems look like roots but can be distinguished by many characteristics.
• The stem of any plant must have nodes and internodes.

• Presence of scale leaves, buds, and adventitious roots at the nodes.
• The internal structure resembles the aerial stem and not the root.

Here are some common types of underground modifications of stems ___


• It is the branch of the main stem.
• It accumulates or stores food in it and swells up.
• The surface of the tuber contains many depressions-like structures known as axillary buds or eyes.

• These axillary buds can grow into new plants under favourable conditions.
Example – Potato, Yam, Taro.


• It is a branched, horizontally growing stem having nodes and internodes.
• The lower portion of the nodes gives rise to adventitious roots.

•  On the node sessile scale leaves are formed that bear bud in their axil.
•  These buds remain dormant, but in ideal condition to give to aerial shoots.
•  Example – Turmeric, Ginger, Fingerroot, Galangal (Thailand Ginger)


• These are spherical, branched vertically growing thick underground stems.
• Corm usually bears reduced internodes.
Example – Crocus bulbs (Saffron), Amorphophallus, Gladiolus 


• In bulb the stem is a highly reduced disc-like structure.
• On this disc are numerous fleshy scaly leaves covering a central terminal bud.
• Both the disc and scaly leaves collectively are called Bulbs.
Example – Onion, Garlic

Modification of Stem
Underground modifications of Stem

Subaerial Modification of Stem

• In Subaerial modifications, The stems are partially aerial and partially underground. Their general characteristics are___

• They have short aerial branches and adventitious roots develop at the nodes.
• The node of the stem can grow into a fully developed plant.
• Their sub-aerial stem modifications are meant for vegetative propagation.
• The plants are known as creepers.

• Here are the 4 types of sub-aerial modification of stems with examples.


• It Grows prostrately on the surface of the soil.
• Stem consists of long internodes.
Example – Cynodon (Doob grass), Hydrocotyle, Oxalis (Wood sorrel)


• In some plants the nodes of horizontally growing underground stem give rise to branches that come out of the soil.
• The lower portion of the nodes gives rise to the roots.
Example – Strawberry, Jasmine, Colocasia.

Modification of Stem
Strawberry Plants Stolon (Image source:


• Suckers are formed from the node of the underground stem.
• Stem and sucker both grow horizontally under the soil.
• But sucker comes up obliquely in the form of the leafy shoot.
• Roots formed from the lower portion of nodes.
Example – Mint, Chrysanthemum.

Modification of Stem
Chrysanthemum Sucker (Image Source:


• Stem consists of thick and short internodes.
• The branches are formed from the main stem
• Each branch is capable of growing as an independent plant after separating from the parent plant
Example – Eichhornia (water hyacinth), Pistia.

Modification of Stem
Eichhornia (water hyacinth) (Image Source: Shutterstock)

Aerial Modification of Stem

• In Aerial modification of stem the stem is modified to perform special functions like climbing, protection, food storage, vegetative propagation, etc. Aerial modifications of stems are classified as follows.


• Axillary buds are modified into coiled, wiry, thin structures called tendrils.
• Tendrils help the plant climb up
Example – Passiflora (Passion flower), Vitis (Grapevine), Groundnut.

Modification of Stem
Passiflora Tendrils (Source Wikimedia Commons)


• In some plants, the stem is modified into a stiff, pointed unbranched or branched structure called Thorn
• Thorn performs a defensive function.
• Thorns are modified axillary or terminal buds and possess vascular supply.
Example – Bell, Lemon, Pomegranate, Ulex, Duranta, Carissa.


• In some plants vegetative buds modify into a swollen structure called Bulbils.
• It separates from the parent plant and on the approach of favorable conditions gives rise to a new plant.
• It is an organ of vegetative reproduction.
Example – Yam, Oxalis


• The term “phylloclade” is derived from the Greek name phylloclades.
• Here phyllo means – leaf and Klados means – branch.

Phylloclades are fleshy and flattened photosynthetic shoots.
• These are usually considered to be modified branches.

• In general, “phylloclade” refers to a portion of a leaf-like stem or branch with multiple nodes and internodes.
• The leaves transform into spine or scales.

• The transformed spine also helps in transpiration. Phylloclades take part.
• Example – Coccoloba, Euphorbia, Opuntia (Prickly pear)


• These are almost similar to Phylloclade, with the difference that cladodes may comprise only one internode.

• These are green cylindrical or flattened leaf-like branches of limited growth.
• They help in photosynthesis.
 Example – Asparagus (cladodes are one Internode long), Ruscus (cladodes are two internodes long)

Modification of Stem
Asparagus (Image Source:

Modification of Stem with examples (Chart)

Modification of Stem with examples
Modification of Stem with examples

Frequently Asked Questions (FAQ)

Q1. Thorn of Citrus is modified___?

Answer: The thorn of citrus is a modified branch or stem, rather than a modified leaf. Citrus trees, which include oranges, lemons, limes, and grapefruits, are characterized by their sharp thorns or spines that grow on their branches and stems.

Q2. Leaves are modified into tendrils in___?

Answer: Leaves are modified into tendrils in many climbing plants, which use these tendrils to attach themselves to structures or other plants for support as they grow. Some examples of plants with tendrils include Peas, Grape Vine, Cucumbers, and Sweet Peas.

Q3. An example of an edible underground stem is__?

Answer: An example of an edible underground stem is the potato (Solanum tuberosum). Potatoes are a type of tuber, a specialized type of underground stem that stores nutrients to support plant growth.

Q4. New Banana plant developed from___?

Answer: A new banana plant developed from the underground stem of a banana plant is called a rhizome.

Q5. What type of stem modification is found in the Mint plant?

Answer: Mint plants (genus Mentha) have a type of stem modification called “Sucker.”

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