Development Of Organisms And Continuity Of Life: Sexual Reproduction In Plants
16.3 Sexual Reproduction In Plants
Flower Structure
| Part | Function |
|---|---|
| Sepals | Protect flower bud |
| Petals | Attract pollinators |
| Stamens (anther + filament) | Male part, produces pollen |
| Carpel (stigma, style, ovary, ovules) | Female part, ovary contains ovules |
- Insect-pollinated flowers: Large colourful petals, nectar, sticky pollen.
- Wind-pollinated flowers: Small petals, exposed stamens/stigmas, smooth light pollen.
Pollination
- Definition: Transfer of pollen from anther to stigma.
- Types:
- Self-pollination → same flower/plant.
- Cross-pollination → between different plants.
Comparison
- Self → no variation, reliable.
- Cross → variation, increases adaptability, but depends on pollinators.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course
Fertilisation
- Pollen grain germinates on stigma.
- Pollen tube grows down style → into ovule.
- Male nucleus fuses with female nucleus → zygote.
- Ovule develops into seed, ovary into fruit.
Seed Structure
- Embryo: Radicle (root), plumule (shoot), cotyledons (seed leaves).
- Testa: Seed coat for protection.
Types Of Seeds
- Monocotyledons → 1 cotyledon, parallel veins, fibrous roots.
- Dicotyledons → 2 cotyledons, net-like veins, tap root.
Seed Germination
- Requires: water, oxygen, suitable temperature.
- Process:
- Water activates enzymes.
- Stored starch → maltose → glucose → energy for growth.
- Radicle emerges first, then plumule.
Written And Compiled By Sir Hunain Zia, World Record Holder With 154 Total A Grades, 7 Distinctions And 11 World Records For Educate A Change O Level And IGCSE Biology Full Scale Course