Reproduction in Plants
1. Modes of Reproduction
| Mode | Description | Examples |
|---|---|---|
| Asexual | Single parent. NO gametes. OFFSPRING are GENETICALLY IDENTICAL to parent (CLONES) | Vegetative propagation, budding, spores |
| Sexual | TWO parents. Gametes FUSE. OFFSPRING show GENETIC VARIATION | Flowering plants |
2. Asexual Reproduction
Budding
A SMALL outgrowth (bud) forms on the parent, grows, and DETACHES to become a new individual. Example: Yeast.
Fragmentation
The parent body BREAKS into two or more fragments. Each fragment grows into a NEW individual. Example: Spirogyra (filamentous algae), some mosses.
Spore Formation
Spores (TINY reproductive cells) are produced in SPORANGIA. Under favourable conditions, they GERMINATE into new plants. Examples: Bread mould (Rhizopus), ferns, mosses.
Vegetative Propagation
A PART of the plant (stem, root, leaf) grows into a NEW plant.
| Method | Description | Example |
|---|---|---|
| Stem cutting | Stem piece planted in soil | Rose, sugarcane, money plant |
| Runner | Creeping stem that ROOTS at nodes | Strawberry, grass |
| Tuber | SWOLLEN underground stem (has 'eyes') | Potato |
| Bulb | SHORT stem with fleshy leaves | Onion, garlic, tulip |
| Rhizome | Horizontal UNDERGROUND stem | Ginger, turmeric |
| Sucker | Stem from UNDERGROUND base | Banana, chrysanthemum |
| Leaf cutting | Leaf placed on soil grows new plant | Bryophyllum (leaf has buds at edges) |
| Grafting | Stem of ONE plant JOINED to root of ANOTHER | Mango, apple, rose |
3. Sexual Reproduction in Flowering Plants
Structure of a Flower
Male parts (ANDROECIUM):
- STAMEN (filament + anther)
- Anther produces POLLEN GRAINS (male gametes)
Female parts (GYNOECIUM):
- PISTIL (stigma + style + ovary)
- Ovary contains OVULES (each ovule has a FEMALE gamete / egg cell)
Other parts:
- Sepals (CALYX) — PROTECT the flower in bud stage
- Petals (COROLLA) — ATTRACT pollinators by colour and scent
- Nectaries — Produce NECTAR (food for pollinators)
4. Pollination
Transfer of POLLEN GRAINS from ANTHER to STIGMA of a flower.
| Type | Description | Examples |
|---|---|---|
| SELF-pollination | Pollen from SAME flower | Pea, wheat, rice |
| CROSS-pollination | Pollen from ANOTHER flower (same or different plant) | Most flowering plants |
Agents of Pollination
| Agent | Adaptations | Examples |
|---|---|---|
| WIND (Anemophilous) | Light, smooth, SMALL pollen. Feathery stigmas | Grasses, maize |
| INSECTS (Entomophilous) | Large, STICKY pollen. Bright petals, scent, nectar | Sunflower, rose |
| BIRDS (Ornithophilous) | Tubular flowers, abundant nectar | Hibiscus |
| WATER (Hydrophilous) | Pollen floats on water | Hydrilla, Vallisneria |
5. Fertilisation
The FUSION of MALE gamete (pollen nucleus) with the FEMALE gamete (egg cell).
Process:
- Pollen grain GERMINATES on stigma → pollen TUBE grows down the style
- Pollen tube enters the OVULE through the micropyle
- MALE nucleus fuses with EGG cell → ZYGOTE
- Zygote develops into EMBRYO
6. Seed Dispersal
The spreading of SEEDS away from the parent plant to REDUCE competition.
| Agent | Adaptations | Examples |
|---|---|---|
| WIND | Light seeds, wings, parachutes, hairs | Dandelion, maple, cotton |
| ANIMALS | Hooks/spines (stick to fur) or fleshy FRUITS (eaten, seeds excreted) | Xanthium, mango, guava |
| WATER | Fibrous coats, air spaces — seeds float | Coconut, lotus |
| EXPLOSION (self) | Pod dries and SPLITS — seeds are THROWN out | Balsam, pea |
Common Mistakes and Fixes
| Mistake | Fix |
|---|---|
| 'All plants reproduce sexually' | Many plants reproduce ASEXUALLY (through runners, tubers, cuttings) and some ONLY asexually |
| 'Fertilisation and pollination are the same' | Pollination is transfer of POLLEN to stigma. Fertilisation is FUSION of male and female GAMETES |
| 'Potato is a root' | Potato is an UNDERGROUND STEM (tuber) with 'eyes' (buds). It is NOT a root |
| 'All flowers have both male and female parts' | Some flowers are UNISEXUAL — only male (staminate) or only female (pistillate). Example: Papaya, cucumber |
ICSE Exam Focus (6–8 marks)
- 2-mark questions: Define pollination, fertilisation, vegetative propagation
- 3-mark questions: Differences between self and cross pollination
- 4-mark questions: Structure of a flower labelled diagram
- 6-mark questions: Seed dispersal — agents and adaptations
Self-Test
Q1. What is vegetative propagation? Give two examples. A1. Vegetative propagation is reproduction using a VEGETATIVE part (stem, root, leaf) of the plant. Examples: Potato (tuber), rose (stem cutting).
Q2. Distinguish between self-pollination and cross-pollination. A2. Self-pollination: pollen from SAME flower lands on its own stigma. Cross-pollination: pollen from ONE flower lands on the stigma of ANOTHER flower (of the same species).
Q3. Label the parts of a flower and state the function of each. A3. Sepals (protect bud), petals (attract pollinators), stamens (produce pollen), pistil (contains ovules, receives pollen).
Q4. Why is seed dispersal important? A4. Seed dispersal REDUCES competition for sunlight, water, and minerals between the parent plant and seedlings. It also helps colonise NEW areas.
Q5. How is a coconut seed adapted for water dispersal? A5. The coconut has a FIBROUS, waterproof outer coat (mesocarp) that traps air, helping it FLOAT. It can travel long distances in water.
Q6. What is the difference between a tuber and a bulb? A6. A tuber (e.g., potato) is a SWOLLEN underground STEM with 'eyes' (buds). A bulb (e.g., onion) has a SHORT stem with FLESHY LEAVES (scales) that store food.
