Chapter 10 — Economically Useful Plants Exercise Solutions
This chapter is memorisation-heavy. Create a table with plant name, family, useful part, and economic value. That structure works well in exam answers.
How to Use This Page
1. Start with the Key Concepts table to quickly review scientific names, families, and active compounds — these are frequent 1-mark questions. 2. Work through the MCQs to test recall of specific plant–product associations. 3. Fill in the Blanks practises exact terminology — scientific names and family names that examiners require. 4. True or False helps identify common misstatements about plant parts and uses. 5. Match the Following reinforces paired facts (plant–compound, plant–family). 6. Answer Briefly gives you 2-mark templates — keep them concise. 7. Answer in Detail provides structured 5-mark answer formats with sub-points. 8. Common Mistakes to Avoid highlights exactly where students lose marks in this chapter. 9. Exam Checklist — use this as a final revision sheet before the exam.
Key Concepts (Quick Recap)
| Term | Definition |
|---|---|
| Cereals | Grass family (Poaceae) grains — rice, wheat, maize — staple food providing carbohydrates |
| Pulses | Legume seeds rich in protein — Bengal gram, red gram, soybean |
| Fibre plants | Plants yielding fibres for textiles and rope — cotton (seed hair), jute (stem bast) |
| Timber | Wood used for construction and furniture — teak, rosewood, sandalwood |
| Latex | Milky white fluid from rubber tree (Hevea brasiliensis), processed into rubber |
| Medicinal plants | Plants with therapeutic compounds — Cinchona (quinine), Rauwolfia (reserpine) |
| Spices | Aromatic plant parts used for flavouring — pepper (fruit), turmeric (rhizome), ginger (rhizome) |
| Beverages | Drinks derived from plants — tea (leaf), coffee (seed), cocoa (seed) |
| Biofuel | Fuel derived from plant biomass — sugarcane ethanol, jatropha biodiesel |
| Gossypium hirsutum | Scientific name of cotton — fibre from seed epidermal hairs |
| Corchorus capsularis | Scientific name of jute — bast fibre from stem phloem |
| Tectona grandis | Scientific name of teak — most valuable timber in India |
| Cinchona officinalis | Source of quinine — antimalarial drug from bark |
| Rauwolfia serpentina | Source of reserpine — antihypertensive and tranquilliser |
| Digitalis purpurea | Source of digitalin — cardiac stimulant for heart conditions |
Major Categories of Economically Useful Plants
| Category | Examples | Useful Part |
|---|---|---|
| Cereals | Rice, Wheat, Maize | Grain (endosperm) |
| Pulses | Bengal gram, Red gram, Soybean | Seed (protein-rich) |
| Sugar plants | Sugarcane, Sugar beet | Stem (cane), Root (beet) |
| Beverages | Tea, Coffee, Cocoa | Leaf (tea), Seed (coffee, cocoa) |
| Fibre plants | Cotton, Jute, Flax | Seed hair (cotton), Stem bast (jute) |
| Timber | Teak, Rosewood, Sandal wood | Wood |
| Rubber | Hevea brasiliensis | Latex (from stem) |
| Medicinal | Neem, Tulsi, Cinchona, Rauwolfia | Various |
| Spices | Pepper, Turmeric, Ginger | Fruit, Rhizome, Seed |
Important Medicinal Plants
| Plant | Scientific Name | Active Compound | Use |
|---|---|---|---|
| Cinchona | Cinchona officinalis | Quinine | Malaria treatment |
| Rauwolfia | Rauwolfia serpentina | Reserpine | Hypertension, tranquilliser |
| Neem | Azadirachta indica | Azadirachtin | Antibacterial, antifungal, pesticide |
| Tulsi | Ocimum sanctum | Eugenol | Cold, cough, antibacterial |
| Aloe | Aloe barbadensis | Aloin | Burns, skin care, laxative |
| Opium poppy | Papaver somniferum | Morphine, codeine | Painkiller, cough suppressant |
| Digitalis | Digitalis purpurea | Digitalin | Heart stimulant |
Fibre Plants — Details
- Cotton (Gossypium hirsutum): Seed hairs are the fibre. India is the second largest producer. Used in textiles, medical (absorbent cotton).
- Jute (Corchorus capsularis): Stem bast fibres. Used in sacking, ropes, carpet backing — biodegradable packaging.
- Flax/Linseed (Linum usitatissimum): Stem bast (flax fibre for linen); seed oil (linseed oil for paint).
Timber Plants
- Teak (Tectona grandis): Most valuable timber in India — ship-building, furniture, railway carriages.
- Sandalwood (Santalum album): Fragrant heartwood for incense, oil; carving.
- Bamboo (Bambusa): "Poor man's timber" — construction, paper pulp.
I. Choose the Best Answer (MCQs)
1. Cotton fibre is obtained from: (a) Stem bast   (b) Seed hairs   (c) Leaf   (d) Root
2. Quinine, used to treat malaria, is obtained from: (a) Neem   (b) Cinchona   (c) Rauwolfia   (d) Digitalis
3. The scientific name of jute is: (a) Gossypium hirsutum   (b) Corchorus capsularis   (c) Tectona grandis   (d) Saccharum officinarum
4. Reserpine, used to treat hypertension, is extracted from: (a) Cinchona   (b) Digitalis   (c) Rauwolfia serpentina   (d) Papaver somniferum
5. Rubber is obtained from the latex of: (a) Tectona grandis   (b) Hevea brasiliensis   (c) Saccharum officinarum   (d) Azadirachta indica
6. "Poor man's timber" refers to: (a) Teak   (b) Sandalwood   (c) Bamboo   (d) Rosewood
7. Rice belongs to the family: (a) Leguminosae   (b) Poaceae   (c) Liliaceae   (d) Solanaceae
8. The active compound azadirachtin is found in: (a) Tulsi   (b) Neem   (c) Aloe   (d) Cinchona
9. Digitalin is used as a: (a) Painkiller   (b) Antimalarial   (c) Heart stimulant   (d) Laxative
10. Jute fibre is obtained from which part of the plant? (a) Seed hairs   (b) Leaf   (c) Stem bast (phloem)   (d) Root
II. Fill in the Blanks
1. The scientific name of teak is Tectona grandis. 2. Cotton fibre is obtained from the seed hairs (epidermal hairs) of Gossypium hirsutum. 3. Quinine is extracted from the bark of Cinchona officinalis. 4. The active compound in Digitalis purpurea used to stimulate the heart is digitalin. 5. Azadirachtin is the active compound in neem with insecticidal properties. 6. Jute fibre is a bast fibre obtained from the phloem of the stem. 7. Hevea brasiliensis is the source of natural rubber, extracted as latex. 8. The family of rice (Oryza sativa) is Poaceae (Gramineae). 9. Morphine and codeine are obtained from Papaver somniferum (opium poppy). 10. Sandalwood (Santalum album) is valued for its fragrant heartwood used in incense and oil.
III. True or False (with corrections)
IV. Match the Following
| Column A | Column B |
|---|---|
| 1. Cinchona | (f) Quinine — antimalarial drug |
| 2. Rauwolfia serpentina | (e) Reserpine — antihypertensive |
| 3. Gossypium hirsutum | (a) Cotton — seed hair fibre |
| 4. Corchorus capsularis | (g) Jute — stem bast fibre |
| 5. Digitalis purpurea | (c) Digitalin — heart stimulant |
| 6. Tectona grandis | (h) Teak — most valuable timber |
| 7. Hevea brasiliensis | (b) Rubber — from latex |
| 8. Azadirachta indica | (d) Neem — azadirachtin, pesticide |
V. Answer Briefly (2-mark)
VI. Answer in Detail (5-mark)
Worked Examples
Example 1 — Plant → economic product
Example 2 — Fibre source comparison (model answer)
Cotton fibre comes from the seed surface (epidermal hairs), while jute fibre is a bast fibre obtained from the phloem of the stem. Both are plant fibres but from different parts.
Example 3 — Oil yielding plants
Common Mistakes to Avoid
- Confusing jute fibre source (bast from stem) with cotton fibre source (seed hair).
- Writing wrong family for rice (correct: Poaceae/Gramineae, not Leguminosae).
- Not giving scientific names when specifically asked.
- Forgetting that rubber is extracted as latex from Hevea brasiliensis bark.
- ❌ "Jute fibre comes from seeds" → ✅ "Jute is a bast fibre obtained from the stem phloem; cotton fibre comes from seed hairs"
- ❌ "Rice belongs to Leguminosae" → ✅ "Rice (Oryza sativa) belongs to Poaceae (Gramineae)"
- ❌ "Digitalis is an antimalarial" → ✅ "Digitalis (Digitalis purpurea) yields digitalin, a heart stimulant; quinine (from Cinchona) is the antimalarial"
- ❌ "Reserpine comes from Cinchona" → ✅ "Reserpine comes from Rauwolfia serpentina; Cinchona yields quinine"
- ❌ "Bamboo is a type of timber tree" → ✅ "Bamboo is a grass (Family Poaceae) called 'poor man's timber' used for construction and paper"
- ❌ "Aloe vera gel is a drug" → ✅ "Aloe vera gel is used topically for burns and skin care; the latex (aloin) is the laxative component"
Exam Checklist
- [ ] Can you name at least 7 categories of economically useful plants with one example each?
- [ ] Can you give the scientific name and family for rice, cotton, jute, and teak?
- [ ] Can you differentiate cotton (seed hair) from jute (stem bast) as fibre sources?
- [ ] Can you list 7 medicinal plants with their active compounds and uses?
- [ ] Do you know the scientific name and active compound for Cinchona, Rauwolfia, and Digitalis?
- [ ] Can you explain the economic importance of rice, cotton, and rubber?
- [ ] Can you distinguish between spices (pepper, turmeric, ginger) and the plant part used?
- [ ] Can you explain how rubber is extracted from Hevea brasiliensis?
- [ ] Do you know the families of key plants — rice (Poaceae), neem (Meliaceae), tulsi (Lamiaceae)?
- [ ] Can you compare fibre sources — cotton vs jute vs flax — with plant parts and uses?
- [ ] Can you give two examples each of timber plants and beverage plants?
- [ ] Can you write the botanical name, family, and active compound for at least 5 medicinal plants?