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Class 7 Science • Chapter 08

Reproduction in Plants

Vardaan Learning Institute • Detailed Chapter Notes

🌸 1. Two Types of Reproduction

🌱 Reproduction in Plants
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ASEXUAL
REPRODUCTION
No flowers, seeds, or pollen involved
Only ONE parent needed
Offspring are genetically identical (clones)
Faster — good for vegetative propagation
SEXUAL
REPRODUCTION
Involves flowers, pollen, seeds
TWO parents (male + female gametes)
Offspring show variation
Involves pollination → fertilisation → seed

🌿 2. Asexual Reproduction — Methods

Method How it works Examples
Vegetative Propagation New plants grow from vegetative parts (stem, root, leaf, bud) Potato (stem tuber), Ginger/Turmeric (rhizome), Onion (bulb), Strawberry (runner/stolon), Bryophyllum (leaf buds/adventitious buds)
Budding A small bud grows on parent organism → detaches to form new organism Yeast (most common example for Class 7)
Fragmentation Parent breaks into fragments → each fragment grows into a new organism Spirogyra (green algae), Hydra (sometimes)
Spore Formation Parent produces thousands of tiny spores → spores disperse (wind, water) → each grows into new plant under suitable conditions Bread mould (Rhizopus), Ferns, Mosses, Mushrooms
Bryophyllum (miracle leaf / sprout leaf plant): A fascinating plant! Tiny plantlets (miniature plants) grow directly on the edges/margins of the leaves from adventitious buds. These tiny plantlets drop off and grow into new plants. You can even place a single Bryophyllum leaf on moist soil and 20–30 new plants will grow from its edges!

🌺 3. Sexual Reproduction — Flowering Plants

Parts of a Flower — The Reproductive Organs

📸 AI Image Prompt
A highly detailed, labeled cross-section of a complete flower showing all reproductive parts. The flower is shown cut open in the center: MALE PARTS (Stamen): Anther (labeled — produces pollen grains; shown as bulbous structure at top), Filament (labeled — thin stalk supporting anther). FEMALE PARTS (Pistil/Carpel): Stigma (labeled — sticky top receives pollen), Style (labeled — tube connecting stigma to ovary), Ovary (labeled — contains ovules which become seeds; drawn as oval structure at base). OTHER PARTS: Petals (labeled — brightly colored to attract pollinators), Sepals (labeled — green leaf-like structures at base), Receptacle (labeled — base of flower), Pedicel (labeled — stalk of flower). A zoom-in inset circle shows a pollen grain magnified. The diagram uses bright colors: yellow/orange for stamens, pink for petals, green for sepals. Educational botanical illustration style on white background with very clear, bold labels and arrows.
Fig. 8.1 — Parts of a flower (male and female reproductive organs)

Flowchart: From Pollination to Seed Formation

Step 1: POLLINATION
Pollen grains from anther → transferred to stigma
Carried by: Wind (grass, maize) / Insects (bee, butterfly) / Water / Animals / Birds
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Step 2: POLLEN TUBE GROWTH
Pollen grain germinates on stigma → grows a tube down style → reaches ovule inside ovary
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Step 3: FERTILISATION
Male gamete (from pollen) fuses with egg cell (ovule) → Zygote formed
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Step 4: SEED AND FRUIT FORMATION
Zygote → Embryo → Seed. Ovary → Fruit. Petals/sepals wither and fall
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Step 5: SEED DISPERSAL
Seeds spread by wind, water, animals, explosive mechanism
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Step 6: GERMINATION
Seed + water + warmth + air → seedling grows → new plant!

🌱 4. Seed Dispersal Methods

Agent Adaptations of seeds Examples
Wind Light, winged (like a parachute or propeller), feathery structures Dandelion (pappus/feathery top), Maple (winged "samara"), Drumstick (Moringa)
Water Light, spongy (waterproof husk to float), buoyant Coconut (husk floats), Lotus
Animals / Humans Hooks, barbs, spines (stick to fur/clothing) OR edible fruit (animal eats fruit, seed passes out in droppings) Xanthium (burs), Goose grass; Mango, Guava (eaten, seed dispersed)
Explosive mechanism Seed pod dries → bursts suddenly, shooting seeds at high speed Balsam (Touch-me-not), Bean, Castor

📝 5. Quick Revision

  1. Asexual: 1 parent, no seeds, clones. Methods: vegetative propagation, budding (yeast), fragmentation (Spirogyra), spore formation (bread mould, ferns)
  2. Sexual: 2 parents, involves flowers. Sequence: Pollination → Fertilisation → Seed → Germination
  3. Stamen = male (anther + filament). Pistil = female (stigma + style + ovary)
  4. Anther produces pollen; Stigma receives pollen; Ovary → Fruit; Ovule → Seed
  5. Pollination agents: wind, water, insects, animals, birds
  6. Fertilisation = male gamete + egg cell → zygote → embryo → seed
  7. Dispersal: Wind (feathery, light), Water (buoyant), Animals (hooks/edible), Explosion (Balsam)
  8. Bryophyllum = leaf buds develop into new plants (asexual)
  9. Budding = yeast reproduces asexually by developing a small bud from parent cell