UPSC Prelims 2007 Q109: Science & Technology – Biology
Which one of the following parts of the pitcher plant becomes modified into a pitcher?
- (a) Stem
- (b) Leaf
- (c) Stipule
- (d) Petiole
Answer: (b) Leaf
Explanation
Pitcher plant — the leaf becomes the pitcher
| Part | Change |
|---|---|
| Leaf lamina (blade) | Becomes the pitcher that holds digestive fluid |
| Leaf apex | Forms the lid |
| Petiole (leaf base) | Becomes flat and leaf-like (does photosynthesis) or a tendril |
Why it traps insects: pitcher plants (e.g., *Nepenthes*) grow in nitrogen-poor soil.
They digest insects to get nitrogen.
They still make food by photosynthesis — so they are partially heterotrophic.
*Nepenthes khasiana* is India's native pitcher plant — found in Meghalaya.
Answer: (b) Leaf.
Why each option is right or wrong
- (a) Incorrect. The stem is not modified into a pitcher.
- (b) CORRECT. The leaf (lamina) is modified into the pitcher; the leaf tip forms the lid.
- (c) Incorrect. Stipules are small outgrowths at the leaf base — not the pitcher.
- (d) Incorrect. The petiole becomes flat or tendril-like, but it is not the pitcher itself.
Key point
Pitcher = modified leaf lamina; lid = leaf apex. Insectivorous plants grow in nitrogen-poor soil.
Remember
The pitcher of a pitcher plant is a modified leaf.
Common mistakes
- Choosing the petiole — it supports the pitcher but is not the pitcher.
- Thinking insectivorous plants cannot photosynthesise — they are green and do photosynthesise.
- Forgetting the reason: nitrogen deficiency.
Exam tip
Insectivorous trio: Pitcher plant (Nepenthes), Venus flytrap (Dionaea), Bladderwort (Utricularia) — all use modified leaves.
Sources
- NCERT Class VII — Science, Ch 1 (Nutrition in Plants)
- NCERT Class XI — Biology, Ch 5 (Morphology of Flowering Plants)