Read the following statements carefully.
A. Leaf base may bear two lateral small leaf like structures called stipules.
B. In dicots, the leaf base expands into a sheath covering the stem partially or wholly.
C. Veins provide rigidity to the leaf blade.
D. In monocots, leaf base is swollen and is known as pulvinus.
E. The petiole help hold the leaf blade to light.
How many of the above given statement (s) is/are incorrect?
Two
— Concept: This question tests the understanding of various morphological features of leaves, including their structure,…Concept: This question tests the understanding of various morphological features of leaves, including their structure, modifications, and functions in both monocot and dicot plants.
Why (A) is correct: We need to identify the incorrect statements among the given options.
Let's analyze each statement:
- A. Leaf base may bear two lateral small leaf like structures called stipules. This statement is correct. Stipules are common in many dicot plants, arising from the base of the petiole.
- B. In dicots, the leaf base expands into a sheath covering the stem partially or wholly. This statement is incorrect. A sheathing leaf base is characteristic of monocotyledonous plants (e.g., grasses, banana), not dicots. In dicots, the leaf base is often just an attachment point or may have stipules.
- C. Veins provide rigidity to the leaf blade. This statement is correct. The vascular bundles (veins) provide structural support and act as a skeleton for the leaf blade.
- D. In monocots, leaf base is swollen and is known as pulvinus. This statement is incorrect. A swollen leaf base called a pulvinus is characteristic of some leguminous plants (dicots), where it is involved in sleep movements (nyctinasty) and turgor movements. Monocots typically have a sheathing leaf base.
- E. The petiole help hold the leaf blade to light. This statement is correct. The petiole (leaf stalk) positions the leaf blade to maximize light exposure for photosynthesis.
Therefore, statements B and D are incorrect. There are two incorrect statements.
Why other options are wrong:
- Option B (Three) is wrong because only two statements (B and D) are incorrect.
- Option C (Five) is wrong because only two statements are incorrect.
- Option D (One) is wrong because two statements are incorrect.
Common Mistake: Students often confuse the characteristics of monocot and dicot leaves, especially regarding the leaf base (sheathing vs. pulvinus) and venation patterns.
NEET Tip: Create a table comparing monocot and dicot leaf features (venation, leaf base, presence/absence of petiole, stipules) for quick revision.
Correct Answer: (A)
Two