By the end of this chapter you'll be able to…

  • 1State the photosynthesis equation in simple terms: Carbon dioxide + Water + Sunlight → Glucose (food) + Oxygen (released)
  • 2Explain that chlorophyll (green pigment) captures sunlight for photosynthesis
  • 3Classify plants: herbs, shrubs, trees, climbers, creepers — with 2 examples each from Tamil Nadu flora
  • 4Differentiate terrestrial and aquatic plants with examples (floating: duckweed; fixed: lotus; underwater: hydrilla)
  • 5Describe 3 plant adaptations: cactus (spines reduce water loss, thick fleshy stem stores water), lotus (waxy waterproof leaves, long hollow stems for air), mangrove (breathing roots/pneumatophores that grow above water)
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Why this chapter matters
Class 4 Plants introduces photosynthesis with the full equation (CO₂ + water + sunlight → glucose + oxygen) for the first time — the most important chemical reaction on Earth. Children learn that plants are the only living things that can make their own food, and that all animal life depends on this process. The chapter also covers plant classification (herbs, shrubs, trees, climbers, creepers), aquatic vs terrestrial plants, and plant adaptations — why cactus has spines instead of leaves, why lotus leaves are waterproof, and why mangroves have breathing roots.

Before you start — revise these

A 5-minute refresher here will save you 30 minutes of confusion below.

Plants — Class 4 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 4 Science, Chapter 7. Plant reproduction and economic uses.


1. About this chapter

This chapter covers Plants as part of the Class 4 Samacheer Kalvi Science curriculum. It deals with plant reproduction and economic uses and builds conceptual understanding essential for the TN School Term Exam.

By the end of this chapter, students will be able to:

  • Describe methods of plant reproduction
  • List economic uses of plants

2. Key concepts

  • Concept 1: Describe methods of plant reproduction.
  • Concept 2: List economic uses of plants.

3. Important terms and formulas

Term / FormulaDescription
Describe methods of plant…Describe methods of plant reproduction
List economic uses of…List economic uses of plants

4. Worked examples

Example 1. Applying a key concept from this chapter.

Solution: Identify the relevant principle → apply the formula or rule → state the answer with correct units.

Example 2. A typical exam-style question on plants.

Solution: Break the problem into steps, use the appropriate formula and verify the answer.

5. Common mistakes

  • Mistake: Skipping units or forgetting to state them. Fix: Always write units alongside every quantity and answer.
  • Mistake: Confusing similar terms or concepts in this chapter. Fix: Make a comparison table of the terms during revision.

6. Practice (exam-style)

  1. Define the main term or principle covered in Chapter 7.
  2. Give two real-life examples related to plants.
  3. Solve a short numerical or descriptive question from this chapter.
  4. State one important formula and explain each symbol.

7. Answer key (hints)

  1. Refer to section 2 (Key concepts) above for the definition.
  2. Examples should be drawn from daily experience and local context.
  3. Apply the formula from section 3, show all steps clearly.
  4. Formula with units — refer to the textbook glossary for symbol meanings.

8. Quick revision

  • Class 4 Science — Chapter 7: Plants.
  • Core idea: Plant reproduction and economic uses.
  • Key outcomes: Describe methods of plant reproduction; List economic uses of plants.
  • Always revise diagrams / tables from the Samacheer Kalvi textbook before the exam.

Key formulas & results

Everything you need to memorise, in one card. Screenshot this for revision.

Photosynthesis
Carbon dioxide (from air) + Water (from roots) + Sunlight energy (captured by chlorophyll) → Glucose (plant food) + Oxygen (released into air). The plant uses glucose for energy and to build other substances (starch, cellulose, proteins).
Photosynthesis literally means 'making things using light'. Without photosynthesis, there would be almost no oxygen in the atmosphere and no food for animals. Plants are the base of every food chain.
Plant adaptations
Desert plants (xerophytes) → cactus: leaves modified into spines (reduce water loss), thick green stem does photosynthesis and stores water. Aquatic plants (hydrophytes) → lotus: broad flat leaves that float, waxy waterproof upper surface, stomata on upper surface only. Mangroves → grow in salty coastal water, have breathing roots (pneumatophores) that come out of the water/mud to take in oxygen, can filter out salt.
Tamil Nadu has the Pichavaram mangrove forest near Chidambaram — one of the largest mangrove forests in India. Mangroves protect the coast from tsunamis and cyclones by absorbing wave energy.
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Common mistakes & fixes

These are the exact errors that cost students marks in board exams. Read them once, save yourself the trouble.

WATCH OUT
Thinking plants 'eat' soil as food
Plants do NOT eat soil. They absorb minerals and water from soil through roots, but their actual FOOD (glucose) is made by the leaves through photosynthesis. Soil provides nutrients, not calories.
WATCH OUT
Thinking photosynthesis happens only during the day
Photosynthesis requires sunlight, so the light-dependent reactions ONLY happen during daylight. But plants also respire (breathe) 24/7 — taking in oxygen and releasing CO₂, just like animals.
Verified by the tuition.in editorial team
Last reviewed on 3 June 2026. Written and reviewed by subject-matter experts — read about our process.
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