ICSE 9 Biology Pollination Short

⚡ Quick Revision: Pollination Types

What is Pollination?

• ✔ The process of transfer of pollen grains from the anther to the stigma.
• ✔ Self-Pollination: Transfer within the same flower or another flower of the same plant.
• ✔ Cross-Pollination: Transfer between flowers of two different plants of the same species.

Feature	Self-Pollination	Cross-Pollination
External Agent	Not required	Required (Wind, Water, Insects)
Genetic Variation	No variation	High variation & healthier offspring

Term Card

Cleistogamy: Pollination occurring in closed flowers that never open (e.g., Commelina).

❌ Don't Confuse:

Autogamy with Geitonogamy. Autogamy is within the same flower; Geitonogamy is between different flowers of the same plant.

⚡ Quick Revision: Agents of Cross-Pollination

Agent	Scientific Term	Flower Characteristics
Insects	Entomophily	Bright petals, scent, nectar, sticky pollen.
Wind	Anemophily	Small, dull, long versatile anthers, feathery stigma.
Water	Hydrophily	Pollens have mucilaginous coating (waterproof).
Birds	Ornithophily	Large, funnel-shaped, bright red/orange.

Contrivances for Cross-Pollination

• ✔ Dichogamy: Anthers and stigma mature at different times (Protandry/Protogyny).
• ✔ Herkogamy: Mechanical barriers prevent self-pollination (e.g., Hood over stigma).
• ✔ Self-Sterility: Pollen of the same flower fails to germinate on its own stigma.

Term Card

Versatile Anthers: Anthers attached at the center so they can swing freely in the wind, common in grasses.

❌ Don't Confuse:

Protandry with Protogyny. Protandry = Anthers mature first; Protogyny = Gynoecium (stigma) matures first.

⚡ Quick Revision: Fertilisation Process

Step-by-Step Fertilisation

• ✔ Pollen Germination: Pollen grain absorbs sugary secretion from stigma and grows a Pollen Tube.
• ✔ Entry into Ovule: The tube carries two male gametes and enters the ovule through the Micropyle.
• ✔ Syngamy: One male gamete fuses with the egg cell to form a Zygote ($2n$).

Pollen Germination & Tube Entry

Floral Part	Post-Fertilisation Fate
Ovary	Fruit
Ovule	Seed
Zygote	Embryo
Integuments	Seed Coats (Testa & Tegmen)

Term Card

Double Fertilisation: Unique to angiosperms; involves Syngamy (forming zygote) and Triple Fusion (forming endosperm).

❌ Don't Confuse:

Pollination with Fertilisation. Pollination is just the transfer; Fertilisation is the fusion of gametes.

⚡ Quick Revision: Post-Fertilisation & Seed Types

The Result: Seeds and Fruits

• ✔ Endosperm: Formed by triple fusion; provides nourishment to the developing embryo.
• ✔ Albuminous Seeds: Seeds where the endosperm is retained (e.g., Castor, Maize).
• ✔ Exalbuminous Seeds: Endosperm is consumed; food is stored in Cotyledons (e.g., Pea, Bean).

Structure	Detailed Function/Definition
Testa	The outer, hard, protective layer of the seed coat.
Tegmen	The inner, thin, papery layer of the seed coat.
Micropyle	Tiny opening that allows water and oxygen entry during germination.

Term Card

Parthenocarpy: The development of fruit without fertilisation; results in seedless fruits (e.g., Banana, Grapes).

❌ Don't Confuse:

Fruit Wall (Pericarp) with Seed Coat. The pericarp comes from the ovary wall, while the seed coat comes from the ovule's integuments.