Topic: Modification of Plant Organs
Subtopic: Leaf, Stem, and Root Modifications
Keyword Definitions:
Thorns: Modified leaves or stems that are hard and pointed, providing protection against herbivores.
Tendrils: Slender, coiled structures developed from leaves or stems that help plants climb.
Cladode: Flattened, photosynthetic stem performing the function of leaves, as in Opuntia.
Pneumatophores: Vertically upward growing roots of certain plants like Rhizophora for gaseous exchange.
Subaerial stems: Stems growing above the ground, aiding in vegetative propagation, as in grasses and strawberry.
Axillary bud: Bud arising from the axil of a leaf, capable of forming branches or tendrils.
Vegetative propagation: Asexual reproduction by non-reproductive plant parts like stems, roots, or leaves.
Lead Question (2022)
Identify the correct set of statements:
(a) The leaflets are modified into pointed hard thorns in Citrus and Bougainvillea
(b) Axillary buds form slender and spirally coiled tendrils in cucumber and pumpkin
(c) Stem is flattened and fleshy in Opuntia and modified to perform the function of leaves
(d) Rhizophora shows vertically upward growing roots that help to get oxygen for respiration
(e) Subaerially growing stems in grasses and strawberry help in vegetative propagation
Options:
(1) (a) and (d) only
(2) (b), (c), (d) and (e) only
(3) (a), (b), (d) and (e) only
(4) (b) and (c) only
Explanation:
In plants, Citrus and Bougainvillea have thorns from modified leaflets, cucumber and pumpkin develop tendrils from axillary buds, Rhizophora grows pneumatophores for oxygen, and grasses and strawberry show subaerial stems for propagation. Opuntia stems are flattened and perform photosynthesis. Correct set is (b), (c), (d) and (e). Answer: (2).
1. Which plant shows modification of leaf into thorns?
(1) Bougainvillea
(2) Cucumber
(3) Opuntia
(4) Strawberry
Explanation:
In Bougainvillea, the leaflets are modified into hard, pointed thorns that provide protection against herbivores. Other plants like cucumber produce tendrils, Opuntia has modified stems, and strawberry shows subaerial stems. Correct answer is (1).
2. Tendrils in cucumber develop from:
(1) Leaves
(2) Axillary buds
(3) Stem
(4) Roots
Explanation:
Cucumber and pumpkin develop slender, spirally coiled tendrils from axillary buds. These tendrils help in climbing and support. Hence, the correct answer is (2).
3. Cladodes are observed in:
(1) Opuntia
(2) Cucumber
(3) Bougainvillea
(4) Grass
Explanation:
Opuntia shows flattened, fleshy stems called cladodes that perform photosynthesis, replacing leaves. Cucumber produces tendrils, Bougainvillea has thorns, and grass has subaerial stems. Correct answer is (1).
4. Pneumatophores are seen in:
(1) Rhizophora
(2) Bougainvillea
(3) Cucumber
(4) Opuntia
Explanation:
Rhizophora develops vertically upward growing roots called pneumatophores that provide oxygen for respiration in waterlogged conditions. Other plants do not show this adaptation. Correct answer is (1).
5. Subaerial stems help in:
(1) Vegetative propagation
(2) Photosynthesis
(3) Respiration
(4) Seed formation
Explanation:
Subaerial stems grow above ground, as in grasses and strawberry, and help in vegetative propagation by producing new plants. They do not primarily perform photosynthesis or respiration. Correct answer is (1).
6. Which plant shows stem modification to perform leaf function?
(1) Opuntia
(2) Bougainvillea
(3) Cucumber
(4) Rhizophora
Explanation:
Opuntia shows flattened, fleshy stems (cladodes) that perform photosynthesis, replacing leaves. Bougainvillea has thorns, cucumber has tendrils, and Rhizophora has pneumatophores. Correct answer is (1).
7. Assertion-Reason MCQ:
Assertion (A): Tendrils are formed from axillary buds in cucumber.
Reason (R): Tendrils help in climbing and provide support.
(1) Both A and R are correct and R explains A
(2) Both A and R are correct but R does not explain A
(3) A is correct but R is false
(4) Both A and R are false
Explanation:
In cucumber, axillary buds develop into tendrils. Tendrils aid climbing and support, which directly explains their formation from axillary buds. Hence, both A and R are correct, and R explains A. Correct answer is (1).
8. Matching Type:
Match the plant with modification:
A. Bougainvillea — 1. Tendril
B. Cucumber — 2. Thorn
C. Opuntia — 3. Cladode
D. Rhizophora — 4. Pneumatophore
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–3, D–4
(3) A–2, B–3, C–1, D–4
(4) A–3, B–2, C–1, D–4
Explanation:
Bougainvillea shows thorns (2), cucumber has tendrils (1), Opuntia shows cladodes (3), and Rhizophora has pneumatophores (4). Correct match is (1).
9. Fill in the Blanks:
________ stems grow above the ground and help in vegetative propagation.
(1) Subaerial
(2) Cladode
(3) Tendril
(4) Rhizophore
Explanation:
Subaerial stems grow above ground, as in grasses and strawberry, and help in vegetative propagation. Cladodes and tendrils have other functions. Correct answer is (1).
10. Choose the Correct Statements:
(a) Bougainvillea shows leaf modified into thorn
(b) Opuntia shows stem modification to perform leaf function
(c) Rhizophora develops pneumatophores
(d) Cucumber and pumpkin produce tendrils from roots
Options:
(1) (a), (b), (c) only
(2) (a), (b), (d) only
(3) All statements
(4) (b) and (d) only
Explanation:
Bougainvillea shows thorns, Opuntia has modified stems, and Rhizophora develops pneumatophores. Tendrils are from axillary buds, not roots. Hence, correct statements are (a), (b), and (c). Correct answer is (1).
Topic: Asexual Reproduction
Subtopic: Vegetative Propagation
Keyword Definitions:
Vegetative Propagation: Type of asexual reproduction using vegetative parts like stem, root, or leaf to form new plants.
Agave: Xerophytic plant that reproduces vegetatively through bulbils.
Bulbil: Small, bulb-like structure that develops on the parent plant and gives rise to new plants.
Rhizome: Underground stem that propagates plants like ginger and turmeric.
Offset: Short lateral shoot that helps water hyacinth multiply rapidly.
Eye: Vegetative bud found on potato tubers for propagation.
Lead Question - 2020 (COVID Reexam)
Vegetative propagule in Agave is as:
1. Rhizome
2. Bulbil
3. Offset
4. Eye
Explanation: In Agave, vegetative propagation occurs through bulbils. These are small bulb-like structures that detach and grow into new plants. Rhizome is used by ginger, offset by water hyacinth, and eye in potato. Thus, the propagule in Agave is bulbil. Answer: Option 2.
1. Which plant propagates through rhizome?
1. Potato
2. Ginger
3. Agave
4. Bryophyllum
Explanation: Ginger propagates vegetatively through rhizomes. Rhizomes are underground stems with nodes and buds that grow into new plants. Potato uses eyes, Agave uses bulbils, and Bryophyllum uses leaf buds. Answer: Option 2.
2. In water hyacinth, the mode of vegetative propagation is:
1. Runner
2. Offset
3. Sucker
4. Tuber
Explanation: Water hyacinth propagates through offsets, which are short lateral branches with nodes that develop roots and new plants. This makes it invasive and called the “terror of Bengal.” Answer: Option 2.
3. Vegetative reproduction in potato occurs through:
1. Rhizome
2. Bulbil
3. Eye
4. Offset
Explanation: Potato tubers propagate vegetatively through eyes, which are axillary buds present on tuber surface. These buds sprout to form new plants. Rhizomes and bulbils belong to other plants. Answer: Option 3.
4. Assertion (A): Bryophyllum reproduces vegetatively through leaf buds.
Reason (R): Adventitious buds on leaf margins of Bryophyllum develop into new plants.
1. Both A and R are true, R is correct explanation
2. Both A and R are true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Bryophyllum reproduces by leaf buds formed along leaf margins. These buds detach, fall on soil, and develop into new plants. Thus both assertion and reason are true, with reason explaining assertion correctly. Answer: Option 1.
5. Match the following:
Column I Column II
(a) Agave (i) Eye
(b) Potato (ii) Offset
(c) Ginger (iii) Bulbil
(d) Water hyacinth (iv) Rhizome
1. (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
2. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
3. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
4. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
Explanation: Agave uses bulbil, potato uses eye, ginger uses rhizome, and water hyacinth uses offset for vegetative propagation. Correct matching is option 1.
6. Fill in the blank:
________ is known as the “Terror of Bengal” because of rapid propagation.
1. Agave
2. Water hyacinth
3. Bryophyllum
4. Potato
Explanation: Water hyacinth multiplies rapidly by offsets and chokes water bodies, causing oxygen depletion and harming aquatic life. Therefore, it is called the “Terror of Bengal.” Answer: Option 2.
7. Choose the correct statements:
(a) Ginger propagates through rhizomes.
(b) Potato propagates through bulbils.
(c) Agave propagates through bulbils.
(d) Bryophyllum propagates through leaf buds.
1. a, c, d only
2. b and c only
3. a and b only
4. a, b, c and d
Explanation: Ginger propagates through rhizome, Agave through bulbils, and Bryophyllum through leaf buds. Potato does not use bulbils but eyes. Therefore, correct statements are a, c, d. Answer: Option 1.
8. Vegetative reproduction in onion is carried out by:
1. Corm
2. Bulb
3. Rhizome
4. Runner
Explanation: Onion reproduces vegetatively through bulbs, which are underground modified stems surrounded by fleshy scales. They sprout into new plants when favorable. Corm belongs to gladiolus, rhizome to ginger, runner to grass. Answer: Option 2.
9. Which vegetative propagule is used by Eichhornia?
1. Offset
2. Runner
3. Corm
4. Bulbil
Explanation: Eichhornia, also called water hyacinth, propagates vegetatively by offsets. This helps rapid spread in aquatic ecosystems, making it invasive. Answer: Option 1.
10. In which plant are adventitious buds present on leaf margins?
1. Bryophyllum
2. Onion
3. Ginger
4. Agave
Explanation: Bryophyllum leaves have adventitious buds along leaf margins that develop into new plants when detached. This is a unique vegetative propagation method in Bryophyllum. Answer: Option 1.
Chapter: Morphology of Plants
Topic: Modifications of Plant Organs
Subtopic: Thorn, Spine, and Prickle Formation
Keyword Definitions:
• Thorn – A sharp pointed modified structure, usually derived from stems or branches for protection.
• Stipules – Small leaf-like appendages at the base of leaf petioles, sometimes modified.
• Adventitious roots – Roots arising from non-root tissues like stems or leaves.
• Bougainvillea – A plant known for its protective thorns derived from modified branches or stems.
• Leaf modification – Adaptation of leaves for storage, protection, or climbing.
• Spine – Modified leaf or part of a leaf serving as a protective structure.
• Prickle – Outgrowth from epidermis or cortex, not vascular in origin.
• Clinical/educational relevance – Knowledge of modifications is important in botany, agriculture, and plant defense studies.
Lead Question – 2017:
In Bougainvillea thorns are the modifications of :
(A) Leaf
(B) Stipules
(C) Adventitious root
Explanation:
In Bougainvillea, thorns are modified stems or branches, not leaves, stipules, or roots. These thorns provide protection against herbivores. The modification involves the hardening and tapering of the shoot axis. Such structural adaptations are significant in plant defense mechanisms. (Answer: B)
1) Which plant part gives rise to spines in cactus?
(A) Leaf
(B) Stem
(C) Root
(D) Stipule
Explanation:
In cacti, spines are modified leaves adapted to reduce water loss and protect the plant. Unlike Bougainvillea, where thorns arise from stems, cactus spines are leaf derivatives. This distinction highlights how plants modify different organs for similar protective functions. (Answer: A)
2) Prickles are derived from:
(A) Epidermis and cortex
(B) Leaf
(C) Stem
(D) Root
Explanation:
Prickles arise from the epidermis and cortex, not vascular tissues, unlike thorns or spines. Roses exhibit prickles, serving as protection against herbivores. Understanding these modifications helps in identifying plant species and studying adaptive morphology. (Answer: A)
3) Which modification is for climbing in plants?
(A) Tendrils
(B) Thorns
(C) Prickles
(D) Spines
Explanation:
Tendrils are modified stems or leaves that allow plants to climb and gain sunlight. Thorns, spines, and prickles primarily serve as protective adaptations. Bougainvillea thorns are not for climbing but defense. Morphological adaptations illustrate plant survival strategies. (Answer: A)
4) Clinical/educational relevance: Thorny plants help in:
(A) Preventing herbivory
(B) Supporting plant structure
(C) Water absorption
(D) Photosynthesis
Explanation:
Thorny structures like in Bougainvillea deter herbivores, reducing damage to leaves and stems. Such modifications are a defense strategy in harsh environments. They do not aid in photosynthesis or water absorption directly but enhance plant survival and reproductive success. (Answer: A)
5) Which is true about Bougainvillea thorns?
(A) Modified leaf
(B) Modified stem
(C) Modified root
(D) Modified flower
Explanation:
Bougainvillea thorns are modified stems arising from branch tips. They are hard, pointed, and protective. Leaf, root, or flower modifications serve different functions. Recognizing organ modifications is important for plant identification and understanding adaptive morphology. (Answer: B)
6) Thorn develops from which tissue in Bougainvillea?
(A) Shoot apical meristem
(B) Root meristem
(C) Leaf primordium
(D) Epidermis
Explanation:
Thorns in Bougainvillea develop from the shoot apical meristem, forming hard, pointed structures at branch tips. This is a stem modification, unlike spines (leaves) or prickles (epidermis/cortex). Such adaptations protect the plant and conserve resources. (Answer: A)
7) Assertion-Reason type:
Assertion (A): Bougainvillea thorns are modified stems.
Reason (R): Thorns arise from the shoot apical meristem and provide protection.
(A) Both A and R are true, and R is the correct explanation of A
(B) Both A and R are true, but R is not the correct explanation
(C) A is true, R is false
(D) A is false, R is true
Explanation:
Both assertion and reason are correct; thorns arise from shoot apical meristems, harden, and serve as protective structures in Bougainvillea. This is a classic example of stem modification for defense. (Answer: A)
8) Matching type:
Match plant with type of modification:
(A) Bougainvillea – (i) Thorn
(B) Cactus – (ii) Spine
(C) Rose – (iii) Prickle
(D) Grapevine – (iv) Tendril
Options:
(A) A-i, B-ii, C-iii, D-iv
(B) A-ii, B-i, C-iv, D-iii
(C) A-iii, B-iv, C-i, D-ii
(D) A-iv, B-iii, C-ii, D-i
Explanation:
Correct matches: Bougainvillea – thorn, Cactus – spine, Rose – prickle, Grapevine – tendril. Identifying modifications aids in studying plant morphology, adaptation, and taxonomy. (Answer: A)
9) Fill in the blanks:
In Bougainvillea, thorns are modifications of ________.
(A) Stem
(B) Leaf
(C) Root
(D) Flower
Explanation:
Bougainvillea thorns are stem modifications. They arise from shoot apical meristems and protect the plant from herbivores. Leaf, root, or flower modifications serve other adaptive purposes. Understanding these helps in botany and plant defense studies. (Answer: A)
10) Choose the correct statements:
1. Bougainvillea thorns are modified stems.
2. Cactus spines are modified leaves.
3. Rose prickles are epidermal outgrowths.
4. Bougainvillea thorns are modified roots.
(A) 1, 2, 3 only
(B) 2, 3, 4 only
(C) 1, 3, 4 only
(D) All are correct
Explanation:
Statements 1, 2, and 3 are correct; Bougainvillea thorns are stems, cactus spines are leaves, and rose prickles arise from epidermis. Statement 4 is incorrect. Recognizing these modifications is essential for morphological studies and understanding plant adaptations. (Answer: A)
Chapter: Plant Physiology
Topic: Plant Adaptations
Subtopic: Modified Plant Organs
Keyword Definitions:
Cladodes: Flattened photosynthetic stems resembling leaves, performing leaf functions in some plants.
Phyllodes: Modified leaf petiole functioning as a leaf blade, often in xerophytic plants.
Phylloclades: Flattened green stem segments acting as leaves, commonly seen in drought-resistant plants.
Scales: Small, reduced leaves that may serve protective functions in plants.
2016 (Phase 1)
Lead Question: Stems modified into flat green organs performing the functions of leaves are known as:
(1) Cladodes
(2) Phyllodes
(3) Phylloclades
(4) Scales
Answer & Explanation: The correct answer is (3). Phylloclades are specialized flattened green stem segments that perform photosynthesis like leaves. They are common in plants adapted to arid environments, reducing water loss while maximizing photosynthetic efficiency. Unlike phyllodes and cladodes, phylloclades are true stem modifications, not leaf derivatives.
Single Correct Answer MCQ: In xerophytic plants, the modified leaf structure that reduces water loss is called:
(1) Phylloclade
(2) Phyllode
(3) Spine
(4) Tendril
Answer & Explanation: The correct answer is (2). Phyllodes are modified petioles that perform the function of leaves, often seen in xerophytes like Acacia. They reduce water loss by having fewer stomata and less surface area, enabling the plant to survive in arid conditions while still performing photosynthesis effectively.
Assertion-Reason MCQ:
Assertion (A): Phylloclades perform photosynthesis like leaves.
Reason (R): Phylloclades contain chlorophyll and have stomata for gas exchange.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.
Answer & Explanation: The correct answer is (1). Phylloclades are green and contain chlorophyll for photosynthesis. Their stomata allow gas exchange, making them functionally equivalent to leaves. This adaptation helps plants survive in water-limited environments by minimizing water loss and reducing reliance on traditional leaves.
Matching Type MCQ: Match the plant modification to its function:
A. Phylloclade 1. Reduces water loss
B. Phyllode 2. Performs photosynthesis replacing leaves
C. Spine 3. Protection from herbivores
D. Tendril 4. Support for climbing plants
(1) A-2, B-1, C-3, D-4
(2) A-1, B-2, C-3, D-4
(3) A-4, B-1, C-2, D-3
(4) A-3, B-4, C-1, D-2
Answer & Explanation: The correct answer is (1). Phylloclades and phyllodes perform photosynthesis, replacing traditional leaves. Spines provide protection against herbivores and reduce water loss. Tendrils provide structural support allowing plants to climb. These modifications help plants adapt to environmental challenges like drought and predation.
Fill in the Blanks / Completion MCQ: The modified stem performing photosynthesis and resembling a leaf is called ________.
(1) Phyllode
(2) Cladode
(3) Phylloclade
(4) Tendril
Answer & Explanation: The correct answer is (3). Phylloclades are specialized flat green stems that carry out photosynthesis in plants where true leaves are reduced or absent. This adaptation helps minimize water loss while allowing efficient energy capture in arid environments, contributing to plant survival under harsh conditions.
Choose the correct statements MCQ:
1. Phylloclades are stem modifications functioning like leaves.
2. Spines are modified roots for protection.
3. Tendrils help in plant support by twining around structures.
4. Phyllodes are modified petioles acting as leaves.
(1) 1, 3, and 4 only
(2) 1 and 2 only
(3) 2 and 3 only
(4) 1, 2, and 3 only
Answer & Explanation: The correct answer is (1). Phylloclades are modified stems performing photosynthesis. Tendrils provide structural support. Phyllodes are modified petioles that function as leaves. Spines, however, are modified leaves or stipules, not roots, aimed at reducing transpiration and deterring herbivores.
Keywords:
Stem modification: Alterations of the stem for specific functions like storage, support, or climbing.
Thorns: Sharp pointed stems for protection.
Tendrils: Slender thread-like stems aiding in climbing.
Phylloclade: Flattened photosynthetic stem.
Pseudobulb: Swollen stem for water storage.
Opuntia: Cactus genus with flattened stems called cladodes or phylloclades.
Nepenthes: Carnivorous plant with modified leaves forming pitcher traps.
Climbing stems: Stems modified as tendrils.
Photosynthetic stems: Flattened to perform photosynthesis.
Defensive structures: Thorns deter herbivory.
Storage stems: Store water and nutrients for survival.
Chapter: Morphology of Angiosperms
Topic: Modification of Organs
Subtopic: Stem Modifications
Lead Question - 2016 (Phase 1): Which of the following is not a stem modification:
(1) Pitcher of Nepenthes
(2) Thorns of Citrus
(3) Tendrils of Cucumber
(4) Flattened structures of Opuntia
Answer: 1
Explanation: Pitcher of Nepenthes is a modified leaf, not stem. Thorns (Citrus), tendrils (Cucumber), and flattened stems (Opuntia) are all examples of stem modifications. Correct identification helps in understanding functional adaptations in plants.
1. Single Correct Answer MCQ: Thorns in plants like Citrus are modifications of:
(A) Leaf
(B) Stem
(C) Root
(D) Flower
Answer: B
Explanation: Thorns in Citrus are modified stems that provide mechanical protection against herbivores and reduce water loss in dry conditions.
2. Single Correct Answer MCQ: Flattened photosynthetic stems are called:
(A) Phylloclades
(B) Tendrils
(C) Thorns
(D) Bulbs
Answer: A
Explanation: Phylloclades are flattened, green stems that carry out photosynthesis in plants like Opuntia where leaves are reduced.
3. Single Correct Answer MCQ: Tendrils in cucumber are modified:
(A) Leaves
(B) Stems
(C) Roots
(D) Flowers
Answer: B
Explanation: Tendrils are modified stems that help climbing plants attach and gain support for vertical growth.
4. Single Correct Answer MCQ: Which stem modification helps in storage of water and nutrients?
(A) Tendrils
(B) Phylloclades
(C) Bulbs
(D) Thorns
Answer: C
Explanation: Bulbs are swollen underground stems that store food and water, enabling plants to survive adverse conditions.
5. Single Correct Answer MCQ: Which modification aids in photosynthesis when leaves are absent?
(A) Thorns
(B) Phylloclades
(C) Tendrils
(D) Roots
Answer: B
Explanation: Phylloclades in plants like Opuntia take over the photosynthetic function when leaves are reduced or absent.
6. Single Correct Answer MCQ: Defensive sharp structures in plants are usually:
(A) Thorns
(B) Tendrils
(C) Bulbs
(D) Phylloclades
Answer: A
Explanation: Thorns are modified stems that provide mechanical protection and reduce herbivory.
7. Assertion-Reason MCQ:
Assertion (A): Tendrils in cucumber are stem modifications.
Reason (R): They help in climbing and support.
(A) Both A and R are true, R is correct explanation of A
(B) Both A and R are true, R is not correct explanation of A
(C) A is true, R is false
(D) A is false, R is true
Answer: A
Explanation: Tendrils are modified stems that coil around objects to provide mechanical support for climbing plants.
8. Matching Type MCQ: Match stem modifications with their function:
1. Phylloclade A. Support
2. Tendril B. Photosynthesis
3. Bulb C. Storage
4. Thorn D. Protection
(A) 1-B, 2-A, 3-C, 4-D
(B) 1-A, 2-B, 3-D, 4-C
(C) 1-C, 2-D, 3-B, 4-A
(D) 1-D, 2-C, 3-A, 4-B
Answer: A
Explanation: Phylloclades perform photosynthesis, tendrils provide support, bulbs store nutrients, and thorns protect plants.
9. Fill in the Blanks: Modified stems that provide mechanical protection are called ________, and slender structures for climbing are ________.
(A) Thorns; Tendrils
(B) Phylloclades; Bulbs
(C) Bulbs; Phylloclades
(D) Tendrils; Thorns
Answer: A
Explanation: Thorns protect plants mechanically while tendrils are modified stems aiding climbing and attachment.
10. Choose the Correct Statements:
(A) Phylloclades are flattened photosynthetic stems.
(B) Pitchers of Nepenthes are stem modifications.
(C) Thorns are defensive stem modifications.
(D) Tendrils are modified stems for climbing.
(1) A, B, C
(2) A, C, D
(3) B, C, D
(4) All are correct
Answer: 2
Explanation: A, C, and D are correct. Pitcher of Nepenthes is a modified leaf, not a stem.