Reproduction in Plants
1. What Is Reproduction?
REPRODUCTION is the process by which living organisms produce NEW individuals of the SAME species.
Types of Reproduction
| Type | Definition | Involves |
|---|---|---|
| Asexual | ONE parent. NO fusion of gametes. Offspring IDENTICAL to parent. | Vegetative parts, spores |
| Sexual | TWO parents. FUSION of male and female GAMETES. Offspring SHOW VARIATION. | Flowers, seeds |
2. Asexual Reproduction in Plants
Vegetative Propagation
New plants grow from VEGETATIVE parts (root, stem, leaf) — NOT from seeds.
| Method | Description | Examples |
|---|---|---|
| Stem cutting | A piece of stem is planted. Roots develop from nodes. | Rose, sugarcane, hibiscus |
| Runners (stolons) | Horizontal stems that grow along ground, develop roots at nodes. | Strawberry, grass |
| Tubers | Swollen underground stems. Each 'eye' grows into a new plant. | Potato |
| Bulbs | Underground bud with fleshy leaves (scales). | Onion, garlic, tulip |
| Rhizomes | Thick horizontal underground stems. | Ginger, turmeric, iris |
| Suckers | Side shoots from the base of the stem. | Banana, pineapple |
| Leaf propagation | New plant grows from leaf margins. | Bryophyllum (leaf edges have buds) |
Advantages of Vegetative Propagation
- FASTER than growing from seed.
- Offspring are IDENTICAL to parent (maintains desirable traits).
- Can reproduce plants that have LOST the ability to produce seeds.
- Plants reach MATURITY faster.
Spore Formation
- Found in ferns, mosses, and fungi.
- SPORES are tiny, single-celled reproductive bodies.
- Under favourable conditions, spores GERMINATE into new individuals.
3. Sexual Reproduction — The Flower
The FLOWER is the REPRODUCTIVE part of a plant.
Parts of a Flower
| Part | Whorl | Function |
|---|---|---|
| Sepals | Calyx (outermost) | Protect the flower in BUD stage (usually green) |
| Petals | Corolla | ATTRACT pollinators (colourful, scented) |
| Stamens (Male part) | Androecium | Produce POLLEN (contain male gametes) |
| Carpel/Pistil (Female part) | Gynoecium | Produce OVULES (contain female gametes) |
Male Reproductive Part — Stamen
- Anther: Produces POLLEN GRAINS.
- Filament: Stalk that holds the anther.
Female Reproductive Part — Carpel/Pistil
- Stigma: STICKY top surface — receives pollen grains.
- Style: Tube connecting stigma to ovary.
- Ovary: Contains OVULES (each ovule has an egg cell / female gamete).
- Ovule: Develops into SEED after fertilisation.
4. Pollination
POLLINATION is the transfer of POLLEN GRAINS from the ANTHER to the STIGMA.
Types of Pollination
| Type | Description | Examples |
|---|---|---|
| Self-pollination | Pollen from the SAME flower lands on its own stigma | Pea, wheat, tomato |
| Cross-pollination | Pollen is transferred to a stigma of ANOTHER flower of the same species | Most flowers |
Agents of Pollination
| Agent | How It Works | Flower Adaptations |
|---|---|---|
| Wind | Pollen is blown by wind | Small, dull flowers. Light pollen. Feathery stigma. (Grass, wheat, corn) |
| Insects (Bees, butterflies) | Insects visit for NECTAR, carry pollen | Bright petals, scent, nectar. Sticky pollen. (Rose, sunflower) |
| Birds | Birds visit for nectar | Large, tubular, brightly coloured flowers |
| Water | Pollen floats on water | Aquatic plants (Hydrilla) |
5. Fertilisation
FERTILISATION is the FUSION of the MALE GAMETE (sperm nucleus from pollen) with the FEMALE GAMETE (egg cell) inside the ovule.
Process
- Pollen grain lands on the STIGMA.
- Pollen grain GERMINATES → grows a POLLEN TUBE down the STYLE.
- The pollen tube reaches the OVARY, then an OVULE.
- The MALE NUCLEUS (sperm) fuses with the EGG CELL → ZYGOTE.
- The zygote develops into the EMBRYO (inside the seed).
After Fertilisation
| Part | Develops Into |
|---|---|
| Ovule → | SEED (contains embryo + stored food) |
| Ovary → | FRUIT (protects seeds, aids dispersal) |
| Petals, sepals, style, stigma → | WITHER and fall off |
6. Seed and Fruit Dispersal
Why Dispersal?
- To reduce COMPETITION with parent plant.
- To COLONISE new areas.
- To ensure species SURVIVAL.
Modes of Dispersal
| Agent | Adaptations | Examples |
|---|---|---|
| Wind | Light seeds, wings, hairs, parachute | Dandelion, maple, cotton |
| Water | Fibrous coat, air spaces, float | Coconut, lotus |
| Animals/Birds | Fleshy fruits (eaten, seeds pass through), hooks/spines (attach to fur) | Mango, cherry, Xanthium (burrs) |
| Explosion (Self) | Pod dries and bursts open, scattering seeds | Pea, bean, balsam |
7. ICSE Exam Focus
| Topic | Marks | Frequency |
|---|---|---|
| Flower parts and functions | 3 marks | Very High |
| Pollination (types and agents) | 2-3 marks | Very High |
| Fertilisation process | 3 marks | High |
| Vegetative propagation methods | 2-3 marks | High |
| Seed and fruit formation | 2 marks | Medium |
| Seed dispersal | 2 marks | Medium |
Common Mistakes
- Calling the stamen the 'female part' (stamen = MALE, carpel = FEMALE).
- Confusing pollination and fertilisation (pollination = pollen to stigma; fertilisation = fusion of gametes).
- Saying the ovary develops into a seed (it develops into a FRUIT; the OVULE develops into a seed).
- Writing that self-pollination is better than cross-pollination — cross-pollination produces MORE genetic variation.
Self-Test (5 Questions)
Q1. Which part of the flower develops into a FRUIT? (1 mark)
- A) Ovule
- B) Ovary
- C) Style
- D) Petal
Q2. 'What is the difference between self-pollination and cross-pollination?' (2 marks)
Q3. 'Name two methods of vegetative propagation.' (2 marks)
Q4. 'What happens after a pollen grain lands on a stigma?' (2 marks)
Q5. 'How are coconut seeds dispersed?' (1 mark)
Answers
A1. B) Ovary (the ovule develops into the SEED). A2. Self-pollination: pollen from the SAME flower falls on its own stigma. Cross-pollination: pollen from ONE flower goes to the stigma of ANOTHER flower of the same species. A3. Stem cutting (rose), runner (strawberry), tuber (potato), bulb (onion), rhizome (ginger). (Any two.) A4. The pollen grain GERMINATES on the stigma, grows a POLLEN TUBE down the style to the ovary. The male nucleus (sperm) travels through the tube and fuses with the egg cell in the ovule (FERTILISATION). A5. By WATER. Coconuts have a fibrous, waterproof coat that allows them to float on water.
