The Stem
The stem is the ascending part of the plant axis that bears branches, leaves, flowers and fruits. These notes on the stem explain its origin from the plumule and its nodes, internodes and buds. They also cover its functions and the features that separate a stem from a root. Every point of the NCERT section on the stem is covered in short points. In NEET, these facts appear inside statement and match-the-list questions on morphology.
- ★ Must learn The stem is the ascending part of the axis bearing branches, leaves, flowers and fruits.
- ★ Must learn The stem develops from the plumule of the embryo of a germinating seed.
- ★ Must learn Node: the region where leaves are borne. Internode: the portion between two nodes.
- The stem bears buds, which may be terminal or axillary.
- A young stem is generally green; later it often becomes woody and dark brown.
- ★ Must learn Main function: spreading out branches that bear leaves, flowers and fruits.
- The stem conducts water, minerals and photosynthates.
- Some stems store food, give support and protection, and help in vegetative propagation.
- ★ Must learn Nodes and internodes, multicellular hairs and a positively phototropic nature separate stems from roots.
1. What is a Stem?
- ★ Exam imp Stem: the ascending part of the plant axis that bears branches, leaves, flowers and fruits.
- ★ Exam imp It develops from the plumule, the embryonic shoot, of the embryo of a germinating seed.
- The root, by contrast, develops from the radicle of the embryo.
- A stem is generally green when young.
- Later it often becomes woody and dark brown.
★ Very important The stem comes from the plumule and the root from the radicle. NEET often swaps these two terms in statement questions.
Plumule Points up, Radicle Roots down. Both words pair with their own initial: P with the shoot that points up, R with the root.
2. Nodes, Internodes and Buds
- ★ Exam imp Nodes: the regions of the stem where leaves are borne.
- Internodes: the portions of the stem between two nodes.
- The stem bears buds.
- A terminal bud lies at the tip of the stem.
- An axillary bud lies in the axil of a leaf, the angle between the leaf and the stem; it can grow into a branch.
| Part | What it is |
|---|---|
| Node | Region of the stem where leaves are borne |
| Internode | Portion of the stem between two nodes |
| Terminal bud | Bud at the tip of the stem |
| Axillary bud | Bud in the axil of a leaf; develops into a branch |
★ Very important Node: the region of the stem where leaves are borne. Internode: the portion between two nodes. Leaves never arise at internodes.
INTERnode = the INTERval between two nodes. A node is the address where a leaf is born.
What is an internode?
Where is an axillary bud found, and what does it form?
What colour is a young stem, and how does an older stem often look?
3. Functions of the Stem
- ★ Exam imp Main function: spreading out branches that bear leaves, flowers and fruits.
- Conduction of water, minerals and photosynthates (food made in photosynthesis).
- Some stems also perform storage of food.
- Some stems give support.
- Some stems give protection.
- Some stems help in vegetative propagation: forming new plants without seeds.
Extra jobs of some stems: "Some Stems Protect Plants" = Storage, Support, Protection, Propagation (vegetative). What the stem conducts: W-M-P = Water, Minerals, Photosynthates.
Extra Depth: Stem modifications (listed in the NEET syllabus).
- Food storage in underground stems: potato, ginger, turmeric and Colocasia; they also help the plant survive unfavourable conditions.
- Stem tendrils, from axillary buds, help climbing: gourds (cucumber, pumpkin, watermelon) and grapevines.
- Thorns, from axillary buds, protect against grazing animals: Citrus and Bougainvillea.
- In arid regions, flattened (Opuntia) or fleshy cylindrical (Euphorbia) green stems carry out photosynthesis.
- Vegetative propagation: underground stems of grass and strawberry spread to new places, and lateral branches of mint and jasmine arch down to touch the soil.
- Pistia, Eichhornia, banana, pineapple and Chrysanthemum also form new plants from lateral branches.
4. Stem versus Root
- Develops from the plumule
- Bears nodes and internodes
- Bears buds, leaves, flowers and fruits
- Has multicellular hairs
- Positively phototropic: grows towards light
- Generally green when young
- Develops from the radicle (primary root)
- No nodes or internodes
- Bears lateral roots
- Bears root hairs formed by epidermal cells
- Grows inside the soil
- Absorbs water and minerals; anchors the plant
- The three features that separate a stem from a root are nodes and internodes, multicellular hairs and a positively phototropic nature.
- An underground stem is still a stem: potato is an underground stem, not a root, because it has nodes.
To decide whether an organ is a stem, look for nodes: leaves or buds at regular points with internodes between them. A root never has nodes.
Stem identity card: N-H-P = Nodes (with internodes), Hairs (multicellular), Phototropic (positive).
- Not every stem is aerial: potato (Solanum tuberosum) has an underground stem.
- Not every stem stays green: many become woody and dark brown with age.
- Storage, support, protection and propagation are done by only some stems, not all.
5. Exam Essentials
Pairs to Match
| List I | List II |
|---|---|
| Stem | Develops from the plumule |
| Root | Develops from the radicle |
| Node | Region where leaves are borne |
| Internode | Portion between two nodes |
| Axillary bud | Grows into a branch |
| Young stem | Generally green |
| Older stem | Often woody and dark brown |
| Photosynthates | Conducted by the stem |
| Potato | Underground stem |
| Stem hairs | Multicellular |
From which part of the embryo does the stem develop?
Define a node.
Name three things the stem conducts.
Which features separate a stem from a root?
6. Quick Revision
- Stem: ascending part of the axis bearing branches, leaves, flowers and fruits.
- Develops from the plumule of the embryo of a germinating seed.
- Nodes bear leaves; internodes lie between nodes.
- Buds are terminal or axillary.
- Green when young; often woody and dark brown later.
- Main function: spreading out branches bearing leaves, flowers and fruits.
- Conducts water, minerals and photosynthates.
- Some stems: storage of food, support, protection, vegetative propagation.
- Stem versus root: nodes and internodes, multicellular hairs, positively phototropic.
- Potato has an underground stem.
7. Solved Examples
List I: A. Node; B. Internode; C. Plumule; D. Axillary bud
List II: I. Gives rise to the stem; II. Develops into a branch; III. Portion between two nodes; IV. Region where leaves are borne
Choose the correct answer.
(A) A-III, B-IV, C-I, D-II
(B) A-IV, B-III, C-I, D-II
(C) A-IV, B-III, C-II, D-I
(D) A-I, B-III, C-IV, D-II
Answer: (B). Leaves are borne at nodes, internodes lie between nodes, the plumule forms the stem and the axillary bud grows into a branch.
A. It develops from the radicle.
B. It conducts water, minerals and photosynthates.
C. All stems store food.
D. It is generally green when young.
E. It bears nodes and internodes.
Choose the correct answer.
(A) A, B and C only
(B) B, C and D only
(C) B, D and E only
(D) A, D and E only
Answer: (C). A is false: the stem develops from the plumule. C is false: only some stems store food. B, D and E are true.
(A) Presence of nodes and internodes
(B) Multicellular hairs
(C) Positively phototropic nature
(D) Presence of cells that divide
Answer: (D). Dividing cells occur in both stems and roots. The other three are the stem's distinguishing features.
Statement II: Potato is an underground part of the plant.
Choose the correct answer.
(A) Both Statement I and Statement II are correct
(B) Both Statement I and Statement II are incorrect
(C) Statement I is correct but Statement II is incorrect
(D) Statement I is incorrect but Statement II is correct
Answer: (A). Potato (Solanum tuberosum) has an underground stem. Being underground does not make an organ a root; nodes make it a stem.
(A) absorption of water from the soil
(B) spreading out branches bearing leaves, flowers and fruits
(C) synthesis of plant growth regulators
(D) anchorage of the plant
Answer: (B). Absorption, anchorage and synthesis of plant growth regulators are root functions.
8. Practice Questions
- What are the features that distinguish a stem from a root?Answer: Nodes and internodes, multicellular hairs and a positively phototropic nature. The stem also bears buds, leaves, flowers and fruits and develops from the plumule.
- The stem develops from the
(a) radicle
(b) plumule
(c) cotyledon
(d) hilumAnswer: (b) Plumule. - Match List I with List II. List I: A. Water and minerals; B. Photosynthates; C. Leaves; D. Older stem. List II: I. Borne at nodes; II. Woody and dark brown; III. Food conducted by the stem; IV. Conducted from the root upwards through the stem.
(1) A-IV, B-III, C-I, D-II
(2) A-III, B-IV, C-I, D-II
(3) A-IV, B-III, C-II, D-I
(4) A-I, B-III, C-IV, D-IIAnswer: (1). Water and minerals are absorbed by the root and conducted by the stem; photosynthates are food; leaves arise at nodes; older stems are woody. - Read the statements. A. Buds may be terminal or axillary. B. Internodes bear leaves. C. Some stems help in vegetative propagation. D. The stem is the descending part of the axis.
(1) A and C only
(2) A, B and C only
(3) B and D only
(4) C and D onlyAnswer: (1). B is false: leaves arise at nodes. D is false: the stem is the ascending part. - Which of these is NOT a function performed by some stems?
(a) Storage of food
(b) Support
(c) Vegetative propagation
(d) Formation of root hairsAnswer: (d). Root hairs belong to the root. - Statement I: A young stem is generally green. Statement II: Every stem stays green throughout its life.
(1) Both correct
(2) Both incorrect
(3) I correct, II incorrect
(4) I incorrect, II correctAnswer: (3). Many stems later become woody and dark brown.
Common Mistakes to Avoid
- Writing that the stem develops from the radicle. Correct: from the plumule.
- Saying leaves arise at internodes. Correct: leaves are borne at nodes.
- Calling the stem the descending part of the axis. Correct: it is the ascending part.
- Treating potato as a root because it grows underground. It is an underground stem.
- Claiming all stems store food or help in propagation. Only some stems do.
- Forgetting photosynthates in the list of what the stem conducts.
- Listing root hairs as a stem feature. Stems have multicellular hairs; root hairs belong to roots.
Frequently Asked Questions
What is a stem in a flowering plant?
The stem is the ascending part of the plant axis. It bears branches, leaves, flowers and fruits. It develops from the plumule of the embryo of a germinating seed, has nodes and internodes, and bears terminal or axillary buds.
What is the difference between a node and an internode?
A node is the region of the stem where leaves are borne. An internode is the portion of the stem between two nodes. Axillary buds also arise at nodes, in the axils of leaves, and can grow into branches.
What are the functions of the stem?
The main function is spreading out branches bearing leaves, flowers and fruits. The stem also conducts water, minerals and photosynthates. Some stems store food, give support and protection, and help in vegetative propagation.
How can you distinguish a stem from a root?
A stem has nodes and internodes, bears multicellular hairs and is positively phototropic, growing towards light. It also bears buds, leaves, flowers and fruits. A root has none of these features and develops from the radicle.
Why is potato considered a stem and not a root?
Potato is an underground stem of Solanum tuberosum. It is a stem because it has nodes, with buds at them. Position alone does not decide the organ: an underground organ with nodes and buds is a stem.
What are photosynthates?
Photosynthates are the food materials made by the plant during photosynthesis. The stem conducts them, together with water and minerals. Students should list all three when asked what the stem conducts.
Is the stem always green?
No. A stem is generally green when young, but it often becomes woody and dark brown later. This change is common in trees and shrubs, whose older stems are covered by a brown, woody layer.
How are questions on the stem asked in NEET?
NEET usually tests the stem inside statement sets and match-the-list questions on morphology. Common points are its origin from the plumule, nodes and internodes, what it conducts, and the features that separate stems from roots.
Previous year questions on The Stem
1 question from past papers, each with a step-by-step solution.
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