Leaf Morphology

Topic: Leaf Morphology

Subtopic: Phyllotaxy and Leaf Modification

• Palmately Compound: A leaf in which leaflets radiate from a single point like fingers on a palm.

• Alternate Phyllotaxy: Arrangement of leaves singly at different heights on stem nodes alternately.

• Opposite Phyllotaxy: Arrangement of leaves in pairs at the same level on opposite sides of stem.

• Leaf Tendril: Modified leaf or leaflet that helps in climbing by twining around support.

• Calotropis: Plant species commonly showing opposite phyllotaxy.

• Alstonia: Plant species with whorled or pinnately compound leaves, not palmately compound.

• Pea: Plant with modified leaf tendrils aiding climbing.

• China-rose: Hibiscus rosa-sinensis, showing alternate leaf arrangement.

• Phyllotaxy: The arrangement of leaves on a stem.

• Leaf Modification: Structural changes in leaves to perform special functions.

• Compound Leaf: Leaf divided into multiple leaflets.

Lead Question - 2022 (Abroad)

Choose the mismatched pair of leaf character with its example:

1. Palmately compound - Alstonia

2. Alternate Phyllotaxy - China-rose

3. Leaf tendril - Pea

4. Opposite phyllotaxy - Calotropis

Explanation: Palmately compound leaves have leaflets radiating from a common point. Alstonia exhibits whorled or pinnately compound leaves, not palmately compound, making it mismatched. China-rose shows alternate phyllotaxy, pea has leaf tendrils, and Calotropis shows opposite phyllotaxy. Correct answer: Palmately compound - Alstonia. Answer: 1

Q1: Which of the following plants has pinnately compound leaves?

1. Alstonia

2. Pea

3. Calotropis

4. China-rose

Explanation: Alstonia has pinnately compound leaves with leaflets arranged along the rachis. Pea has simple leaves modified as tendrils, Calotropis and China-rose have simple leaves. Answer: Alstonia. Answer: 1

Q2: Leaf tendrils are adaptations for:

1. Water storage

2. Climbing

3. Photosynthesis

4. Reproduction

Explanation: Leaf tendrils are modified leaves or leaflets that wrap around supports, helping the plant climb and gain access to sunlight. Pea plant demonstrates this adaptation. Answer: Climbing. Answer: 2

Q3: Which type of phyllotaxy is observed in China-rose?

1. Opposite

2. Alternate

3. Whorled

4. Palmate

Explanation: China-rose exhibits alternate phyllotaxy where single leaves arise alternately at successive nodes on the stem. This helps optimal light capture and air circulation. Answer: Alternate. Answer: 2

Q4: Calotropis leaves are an example of:

1. Pinnately compound

2. Leaf tendrils

3. Opposite phyllotaxy

4. Whorled phyllotaxy

Explanation: Calotropis leaves are arranged in pairs at each node, representing opposite phyllotaxy. This arrangement ensures efficient light absorption. Answer: Opposite phyllotaxy. Answer: 3

Q5: Palmately compound leaves are characterized by:

1. Leaflets arranged along a central axis

2. Leaflets radiating from a single point

3. Single undivided leaf blade

4. Modified for climbing

Explanation: Palmately compound leaves have multiple leaflets radiating from a common point like fingers from a palm. Examples include Hibiscus and cotton. This arrangement differs from pinnately compound leaves. Answer: Leaflets radiating from a single point. Answer: 2

Q6: Which of the following plants has simple leaves?

1. Alstonia

2. Pea

3. Calotropis

4. None of these

Explanation: Calotropis has simple leaves, China-rose also has simple leaves. Alstonia has pinnately compound, and pea leaves are modified as tendrils. Answer: Calotropis. Answer: 3

Q7: Assertion (A): Leaf tendrils help in climbing.
Reason (R): Tendrils are modified stems or leaves.

1. A is correct but R is not correct

2. A is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: Leaf tendrils are modified leaves that coil around supports, aiding climbing. Both assertion and reason are correct, and the modification explains the climbing function. Answer: Both A and R are correct and R explains A. Answer: 3

Q8: Match the plant with its leaf type:

1. Pea    A. Leaf tendril
2. Calotropis    B. Opposite simple leaf
3. Alstonia    C. Pinnately compound leaf
4. China-rose    D. Alternate simple leaf

1. 1-A, 2-B, 3-C, 4-D

2. 1-C, 2-D, 3-A, 4-B

3. 1-B, 2-A, 3-D, 4-C

4. 1-D, 2-C, 3-B, 4-A

Explanation: Pea has leaf tendrils, Calotropis shows opposite simple leaves, Alstonia has pinnately compound leaves, and China-rose exhibits alternate simple leaves. Correct match: 1-A, 2-B, 3-C, 4-D. Answer: 1

Q9: Leaves arising singly at successive nodes are called _______.

1. Opposite

2. Alternate

3. Whorled

4. Palmate

Explanation: Alternate leaves arise singly at successive nodes, allowing maximum light capture and reducing shading of lower leaves. China-rose shows this arrangement. Answer: Alternate. Answer: 2

Q10: Select correct statements about leaf types:

1. Palmately compound leaves radiate from a single point

2. Pinnately compound leaves have leaflets along a central axis

3. Leaf tendrils aid climbing

4. Calotropis shows alternate phyllotaxy

Explanation: Statements 1, 2, and 3 are correct. Calotropis exhibits opposite, not alternate phyllotaxy. Answer: 1, 2, 3