Stems of many plants are modified to perform different functions such as storage, protection, photosynthesis, support, propagation and perennation. Modifications help in better adaptation and survival. Stems develop from the plumule of the germinating seed. It bears leaves, fruits, flowers, etc. The characteristic feature of a stem is nodes and internodes. The main function of the stem is to support other parts of the plant and conduction of food, water and minerals. In some plants, stems are modified, which can be aerial, subaerial or underground modifications. They are modified to perform other functions, which are not normally associated with the stem.

1. STEMS
STRUCTURE
AND
MODIFICATION
Dr. Manoj Joshi
Department of Botany
KCMT Bareilly

2. Introduction
• Stems of many plants are modified to
perform different functions such as
storage, protection, photosynthesis,
support, propagation and perennation.
Modifications help in better
adaptation and survival.
• Stems develop from the plumule of
the germinating seed. It bears leaves,
fruits, flowers, etc. The characteristic
feature of a stem is nodes and
internodes. The main function of the
stem is to support other parts of the
plant and conduction of food, water
and minerals.
• In some plants, stems are modified,
which can be aerial, subaerial or
underground modifications. They are
modified to perform other functions,
which are not normally associated
with the stem.

3. Table of Contents:
Underground
Stem
Modifications
Subaerial
Stem
Modifications
Aerial Stem
Modification

4. 1. Underground Stem Modifications
• As the name suggests, these are present underground. They serve various purposes such as storage of food, propagation and
perennation. They can be identified from roots by the presence of nodes and internodes. They help in propagation through
asexual reproduction and help the plant survive a period of dormancy. They provide protection from grazing by animals and
environmental stress.
1. Rhizome – It runs parallel to the ground, the upper portion can produce scaly leaves and the bottom portion can give rise to
adventitious roots. They contain, nodes, internodes and buds.They store food.Examples: Ginger, turmeric.Banana contains
rootstock, which is rhizome growing vertically.
2. Bulb – Stem is reduced and surrounded by scale leaves, modified bulbs can be seen.Examples: Tulips, Lilies, Daffodils, Onion,
Garlic
3. Corm – It is a short upright stem, covered with scaly leaves. It is hard as compared to bulbs.Examples: Colocasia, Yam, Saffron
4. Tuber – Here the terminal of the stem is fleshy and stores food. The stem contains nodes and internodes but due to swelling, they
are not very distinct. Presence of scaly leaves at nodes can be seen as eyes or scars.Examples: Potato, Artichokes

5. Rhizome

6. Bulb

7. Corm

8. Tuber

9. 2. Subaerial Stem Modifications

10. Runner

11. Stolon

12. Sucker
Chrysanthemum, banana, pineapple

13. Offsets: Pistia, Eichornia

14. 3. Aerial Stem Modification
• In some plants, the aerial part of the stem and buds get modified to perform various functions such as support, climbing,
photosynthesis and vegetative propagation.
1. Tendrils – These are coiled and a delicate part, which are used for climbing. They develop from the axillary bud. Examples:
grapevines, watermelons, pumpkin, cucumber
2. Thorns – These are developed from axillary buds. They are pointed, woody and hard, spiny structures, which provide protection
from grazing animals. Examples: Bougainvillea, lemon
3. Bulbils – It is a modified axillary bud, it stores food and becomes fleshy. It detaches from the mother plant and develops into a
new plant. Examples: Dioscorea
4. Cladode and Phylloclade – These are modified stems, which are green and perform photosynthesis. They become fleshy.
Leaves are reduced to spines. These are commonly found in xerophytic plants to reduce water loss. Examples: Opuntia,
Euphorbia, Asparagus

15. Tendrils: grapevines, watermelons,
pumpkin, cucumber

16. Thorns
Bougainvillea, lemon

17. Bulbils: Dioscorea

18. Cladode and Phylloclade: Opuntia,
Euphorbia, Asparagus

19. Frequently Asked Questions
• What is a stem?
• The stem is the part of the plant which is found above the ground. The bark of trees are brown in colour and younger
stems are green in colour. It forms the basis of the shoot system and bears leaves, fruits and flowers.
• What are nodes and internodes?
• Nodes and internodes are two major parts of the stem. The nodes hold buds, leaves, branches, etc. Sometimes even
adventitious roots develop from the nodes. The internode is a region between two nodes.
• What are some functions of the stem?
• Stem provides support for the elevation of flowers, leaves and fruits. It stores nutrients and also helps in transportation.
Stems have meristems that help in the production of new living tissue.