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Tamil Nadu (TNBSE)Class 5 Science★ 5-6 marks in TN Class 5 Term 2 exams — seed dispersal, vegetative propagation, and agriculture steps

Plants

Samacheer Kalvi (TN State Board) Class 5 Science — Chapter 7, Plants. Photosynthesis and plant responses. Study notes, key concepts, worked examples, practice questions and quick revision for exam preparation.

⏱ 12 min readMedium difficulty✓ Free · NCERT-aligned

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

1Explain sexual reproduction in plants: flower → pollination (pollen transferred to stigma) → fertilisation (pollen and ovule fuse) → fruit and seed formation
2Explain vegetative propagation: growing a new plant from a vegetative part — stem cutting (sugarcane, rose, hibiscus), root (sweet potato, dahlia), leaf (bryophyllum/air plant — baby plants grow on leaf margins)
3Describe 4 seed dispersal methods with adaptations: wind (light seeds with wings/hairs — dandelion, cotton, maple), water (fibrous husk for floating — coconut, lotus), animals (fleshy fruits eaten — mango, guava; hook-like structures — xanthium, tiger claw), explosion/self-dispersal (pods burst open — pea, balsam, castor)
4List the steps of agriculture in order: ploughing/tilling → sowing seeds → adding manure/fertilisers → irrigation (watering) → weeding (removing unwanted plants) → harvesting (cutting mature crop) → threshing (separating grains) → storage (protecting from pests and moisture)

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Why this chapter matters

Plants in Class 5 bridges biology and agriculture — two subjects deeply connected in Tamil Nadu's agrarian economy. Children learn how plants reproduce both sexually (flowers, pollination, seeds) and asexually (vegetative propagation — growing a whole new plant from a stem cutting, root, or even a leaf). They study the ingenious ways seeds travel — wind (dandelion parachutes), water (coconut floats across oceans), animals (mango seeds hitch a ride in animal stomachs), and explosion (pea pods burst open). The chapter culminates in the steps of agriculture — from ploughing to harvesting — connecting classroom science to the rice fields of the Cauvery delta and the sugarcane farms of Coimbatore.

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Plants — Class 5 Science (Samacheer Kalvi)

TN State Board (Samacheer Kalvi) Class 5 Science, Chapter 7. Photosynthesis and plant responses.

1. About this chapter

This chapter covers Plants as part of the Class 5 Samacheer Kalvi Science curriculum. It deals with photosynthesis and plant responses and builds conceptual understanding essential for the TN School Term Exam.

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

Explain the process of photosynthesis
Describe how plants respond to stimuli

2. Key concepts

Concept 1: Explain the process of photosynthesis.
Concept 2: Describe how plants respond to stimuli.

3. Important terms and formulas

Term / Formula	Description
Explain the process of…	Explain the process of photosynthesis
Describe how plants respond…	Describe how plants respond to stimuli

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)

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

7. Answer key (hints)

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

8. Quick revision

Class 5 Science — Chapter 7: Plants.
Core idea: Photosynthesis and plant responses.
Key outcomes: Explain the process of photosynthesis; Describe how plants respond to stimuli.
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.

Seed dispersal — why and how

Why dispersal? If all seeds fell under the parent plant, they would compete for sunlight, water, and nutrients — and most would die. Dispersal gives seeds a chance to grow in new places. How? Wind dispersal → seeds are light, have wings (maple), hairs (dandelion, cotton), or are dust-like (orchids). Water dispersal → seeds have fibrous waterproof husk (coconut) that floats for months, traveling across oceans. Animal dispersal → fleshy fruits (mango, guava, fig) are eaten; seeds pass through the digestive system and are deposited elsewhere with natural fertiliser. Some seeds have hooks (xanthium/ottara mul) that stick to animal fur. Explosion/self-dispersal → pods dry and burst, flinging seeds away (pea, balsam/gulab jamun, castor, ladys finger).

A coconut can float in the ocean for up to 3 months and still germinate when it washes ashore. This is how coconut palms spread across tropical coastlines worldwide.

Vegetative propagation

Stem cuttings → cut a healthy stem just below a node (where leaves attach), plant in moist soil, roots grow from the node, new plant develops. Plants grown this way: sugarcane, rose, hibiscus, bougainvillea, money plant, grapevine. Root propagation → tuberous roots with buds grow into new plants: sweet potato, dahlia. Leaf propagation → bryophyllum (miracle leaf/air plant): tiny plantlets grow along the leaf margins; when they fall on soil, they root and grow.

Advantage of vegetative propagation: the new plant is genetically IDENTICAL to the parent (clone). This means desirable traits — sweetness in sugarcane, colour in roses — are preserved exactly. Seed-grown plants may vary.

Agriculture steps (from field to table)

1. Ploughing/Tilling → loosening and turning the soil using a plough or tractor; helps aeration and water absorption. 2. Sowing → placing seeds in the soil at the right depth and spacing. 3. Adding Manure/Fertilisers → providing nutrients (NPK — Nitrogen, Phosphorus, Potassium). 4. Irrigation → watering crops through canals, wells, drip irrigation, or sprinklers. 5. Weeding → removing unwanted plants (weeds) that compete with crops. 6. Harvesting → cutting and gathering the mature crop. 7. Threshing → separating grains from the stalk (manually or with machines). 8. Storage → keeping grains in dry, pest-free conditions (silos, gunny bags).

Tamil Nadu's major crops: rice/paddy (Cauvery delta — Thanjavur, Tiruvarur, Nagapattinam), sugarcane (Coimbatore, Erode), cotton (Virudhunagar, Tirupur), groundnut (Vellore, Tiruvannamalai), and banana (Tiruchirappalli). The state has 3 cropping seasons: Kuruvai (June-Sep), Samba (Aug-Jan), and Navarai (Dec-Mar).

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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 vegetative propagation is 'unnatural' or 'GMO'

✓ Vegetative propagation is completely natural. Many plants reproduce this way in the wild — bryophyllum drops its leaf-plantlets naturally, and underground stems (rhizomes of ginger, turmeric) spread and produce new shoots. Humans just learned to use this natural ability.

WATCH OUT

✗ Confusing pollination and fertilisation

✓ Pollination = transfer of pollen from stamen (male) to stigma (female) of a flower. It is like 'delivering the package'. Fertilisation = fusion of the male gamete (from pollen) with the female gamete (ovule) to form a zygote. It is like 'opening the package and using the contents'. Pollination happens BEFORE fertilisation.

WATCH OUT

✗ Thinking all fruits that float are water-dispersed

✓ A coconut floats and IS water-dispersed. But an apple also floats — yet apples are DISPERSED BY ANIMALS that eat them. The method depends on the plant's evolutionary adaptation, not just whether it floats.

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